Galaxy Geode cake

Galaxy Geode Cake

Galaxy cakes, metallic accents, and the never-ending geode cake trend...

....if you love any or all of those things, then THIS is the cake for you! 

Why make this galaxy geode cake? 

I won't lie; this one takes several steps to come together - but once it's done it is a SHOWSTOPPER! 
I used spray-on colors to get that 'galaxy color' effect on the outside - this means you don't have to add so much color to the frosting, so it doesn't alter the taste much. 
This recipe features coconut rum, blue curacao, and some grenadine - inspired by a purple 'galaxy' cocktail - to the cake batter and as a drizzle after baking for an extra kick of flavor. If that's not your style though (or you're serving to an under-21 crowd) just replace them with buttermilk in the cake batter and leave out the drizzle. 

Cake tips! 

Tip 1! Airbrushing is SO fun; don’t let it intimidate you! 😉 Links to the tools I used are below; my entire kit when I did my first cake was less than $60! But cake sprays will work if you're not feeling the airbrush. 

Tip 2! Confession time…I tried ONE geode cake as a brand new baker thinking just using colored rock candy would work…? Nope! It looked frickin awful. I’d show you a picture but I couldn’t find one, so I either took none or deleted them all. :/ Learn from my mistakes and color the rock candy AFTER you put it on the cake! 

Tip 3! Don’t be intimidated by the tiers! They’re really as simple as cutting down a few straws, stuffing them into the cake layers, and then lining up the top cake over your center straw. 😉 However, if you’d rather just do a single cake, here’s a link to a scaled recipe for my favorite Vanilla Cake Layers!


Do I have to make the cake / frosting from scratch? 
  • Absolutely not if you don't want to! You can substitute 3 of your favorite cake mixes plus the ingredients the mix calls for; keep the baking pans the same! (Replace 1 cup of the liquid with 1/3 cup each rum, blue curacao, and grenadine, and add gel colors after mixing if desired!) 
    Store bought frosting is usually a little thinner than my recipe; add a 1/4 cup of extra powdered sugar at a time until you reach a consistency that spreads and stays in place on the cake well. 

Can I make the cake / frosting ahead of time? 
  • Definitely! Wrap the cake layers well and refrigerate up to 4 days or freeze up to 4 months. Transfer the frosting to a zip-lock bag and squeeze out the extra air, and again - refrigerate up to 4 days or freeze up to 4 months.  Thaw in the refrigerator. (I don't recommend freezing this cake once decorated because the colors are likel to run as the cake thaws). 
    On a related note – cover any remaining cake well after serving to keep it from drying out - it will keep at room temperature for 2-3 days or in the fridge for 3-5 days. 

(Disclosure: As an Amazon associate I may earn from qualifying purchases, and my posts often contain affiliate links. If you click a link and make a purchase, I may receive a commission at no extra cost to you!) 

Galaxy Geode Cake pinterest pin

Galaxy Geode Cake

Grab some edible cake spray (or an airbrush if you're feeling fancy)! Here's the recipe you need to make a showstopping Galaxy Geode Cake!
Prep Time30 minutes
Cook Time37 minutes
Decorating time45 minutes
Total Time1 hour 52 minutes
Course: Dessert
Cuisine: American
Keyword: Geode Cake, Galaxy Geode Cake, Tiered Geode Cake
Servings: 24 servings
Calories: 755kcal
Author: Sarah H



Galaxy Geode Cake layers

Cream Cheese Buttercream frosting

  • 12 oz cream cheese (1 1/2 packages; softened)
  • 1 ½ cup three sticks butter, softened (3 sticks, softened)
  • 9 cups powdered sugar
  • 1 Tablespoon clear vanilla extract
  • ¼ teaspoon salt if using unsalted butter
  • 3-5 Tablespoons whipping/heavy cream
  • 2-3 drops black gel food color

Cake drizzle (optional)

  • 1/3 cup Malibu Coconut Rum
  • 1/3 cup blue Curacao
  • 1/3 cup grenadine


  • Rock candy crystals (I also found a pair of tweezers handy for placing rock candy into the ‘geode’ base)
  • Edible silver leaf (I bought mine from Gold Leaf Factory via Amazon)
  • Silver sprinkle mix (optional; to add sprinkle ‘stars’ to the cake)


Cake layers

  • Preheat oven to 350°F. Prepare three 8-inch cake pans and two six-inch cake pans with baker’s floured cooking spray, or grease and line with parchment rounds.
  • Mix together all dry ingredients (flour, sugar, baking powder, and salt) in a stand mixer with a paddle until fully combined. Mix bits of room-temperature butter slowly into the dry mix, on a low speed. Continue to mix until no large chunks of butter remain, and the mixture becomes crumbly.
  • Pour in egg whites and mix on low until just incorporated. Mix in the buttermilk, rum, blue curacao, and grenadine on a low speed. Add in vanilla and oil, and mix on low until fully incorporated. Scrape down the sides of the bowl with a spatula, then beat on medium speed for about 30 seconds.
  • Divide batter evenly between the prepared cake pans (I find a kitchen scale helpful for this part – I had 675g in my large pans and about 450 in my smaller ones). This guarantees your layers will bake to be the same height.
  • Time to add in the colors! With a toothpick, skewer, or butter knife, add a drop of two of each gel color to each cake pan, and swirl them together with a butter knife.
  • Bake for 34-37 minutes, (or until a toothpick comes out clean). Allow cake layers to cool for 10-15 minutes on a wire cooling rack before removing from pans. Place cake layers into the freezer for 45 minutes, to accelerate the cooling process.
  • Once the layers have fully cooled, they can be leveled and any caramelized bits can be trimmed from the sides / top of the cake using a serrated knife if desired. Be sure the layers are completely cooled or chilled before trimming. If you try to trim the layers while they’re still warm, they will crumble apart. (This is a great time to make your frosting!)

Cream Cheese Buttercream frosting

  • Beat together softened cream cheese and butter; slowly add in powdered sugar alternating with milk until frosting reaches desired consistency. Add vanilla, gel color, and salt if needed and beat until well combined.


  • (I wanted a bit more liqueur kick to my cake layers, so I used a squeeze bottle to infuse each one with a few tablespoons of the rum/curacao/grenadine mix above. Optional but delicious! ;) )
  • Place a smear of frosting on your large cake circle (to keep the cake from sliding while you decorate it) and center your large first cake layer in the center of the circle. Spread the layer with frosting). Add your next cake layer on top, and repeat the process with your remaining cake layers.
  • Next, repeat the same process with your smaller cardboard circle and cake layers. Of note – if your circles aren’t pre-center-punched, be sure to grab a dowel or straw and make your own hole in the exact center of the circle! This will allow you to easily center the tier on the base tier later on.
  • Now you're ready to crumb-coat . If you're unfamiliar with crumb-coating, it's just what it sounds like – spreading a thin layer of frosting over the entire outside of the cake tiers to keep crumbs out of your final layer.
  • Once your crumb coat has set (this takes about 5-10 minutes in the fridge), add your final layers of frosting and smooth. I like to use a large offset spatula and pastry cutter/bench scraper for this part.
  • (For my larger tier, I was able to smooth the frosting fairly well free-handed, but I struggled getting the sides smoothed on my smaller one. Trimming the layers just smaller than the cake circle and using the cardboard as a guide for my bench scraper worked well for smoothing the frosting on the top tier!)

Okaaay. The stacking process!

  • How to Make a Tiered Cake’ by Chelsweets is still my favorite video tutorial to date – sometimes seeing the process can be very helpful!
  • Basically, doweling a tiered cake is done to ensure that the top tier doesn’t sink into the lower tier, as well as keeping it centered. I used four shorter cut-to-height plastic straws for my base tier dowels, and one taller one cut at an angle in the center to hold my top tier in place.
  • Grab your ruler for this next part! Push the straws/dowels (cut to the height of the cake) down into the base tier just over one inch from the cake edge, placing them evenly at quarter intervals around the cake. Place your last, tallest straw or dowel into the exact center of the cake, making sure to keep it straight up as you press down. Now you’re ready – center the hole in the bottom of your top tier cake circle over the tallest dowel and let the top tier gently down onto the base tier. The dowel will poke into the center of the top tier to hold it in place.
  • (I could still see my cardboard cake circle a bit, so I covered it up with some rock candy.)

Cutting the geode

  • Cut a slanted geode shape out of the side of the cake - I shot for about 1” from the top and 1” from the cake base for the ends, and made two cuts connecting my end points. I made the opening deepest toward the center, probably 1 ½” at its deepest. (Feel free to eat the cake scraps!) I had to use a pair of scissors to cut out a bit of the 6" cake circle too.
  • With an offset spatula, re-crumb-coat the geode ‘hole.’ (This will keep crumbs in and later hold your rock candy in place.)

Now the most fun part! The galaxy colors!

  • (I used this airbrush kit (surprisingly inexpensive; it’s a great airbrush kit for a beginner) but it's quicker and less expensive to use edible cake sprays.)
  • Spray colors onto the side of the cake - I started with blue, then purple, then black, and finished with silver. Let each color dry 5+ minutes between coats if you’ve put a lot of color on; too much and it will drip and ruin your ‘galaxy’ look!

Finishing the geode

  • Once your cake is colored, press rock candy crystals into the frosting to cover the base of the geode ‘hole.’ I found tweezers handy for reaching the deeper parts.
  • To color the geode, use a bit of airbrush color or dispense some cake spray into a small bowl and brush into the center/deepest part of the geode. Add the most color at the center and make it progressively lighter toward the outer edges. I added more silver with a brush along the outer edge.
  • Rim the outside of the geode with bits of edible silver leaf – I tried a few methods for transferring it, because it’s a bit fragile and finicky. Tearing off and moving bits at a time with a paintbrush has been my favorite method so far!
  • With your paintbrush and a bit of metallic silver paint or lustre dust, add a few ‘flicks’ of silver spray onto the cake. Finish it off with a few silver sprinkle constellations and some silver rock candy around the tier bases – and you’re done!
  • Seriously; find someone to give you a high-five on your kick-butt cake! 😉



Small paring knife (to make the geode cut in the side of the cake
5 large straws or cake dowels
OR you can use blue, purple, black, and silver edible cake sprays!


Serving: 1slice (1/24th cake) | Calories: 755kcal | Carbohydrates: 98g | Protein: 8g | Fat: 37g

Did you make this Galaxy Geode Cake? 

Let me know how it went – or make my day and find me on Pinterest or on Instagram and tag @IntensiveCakeUnit in your photo! 
You can also leave a comment or recipe rating at the bottom of the page! 

Cream Cheese Buttercream Frosting

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