Buttercream Galaxy Cake That's Pure Magic

Name: Buttercream Galaxy Cake That's Pure Magic
Prep time: 30 min
Cook time: 30 min
Total time: 1 h
Cuisine: American
Ingredients: 2 ½ cups all-purpose flour; 2 ½ tsp baking powder; ½ tsp salt; ½ cup unsalted butter, softened; ½ cup vegetable oil; 1 ¾ cups granulated sugar; 4 large eggs; 1 cup sour cream; 2 tsp pure vanilla extract; ¾ cup whole milk; 2 cups unsalted butter, softened (for frosting); 6 cups powdered sugar; 2 tsp vanilla extract; 4 tbsp heavy cream; Gel food coloring (pink, purple, blue, black); 1 tbsp black cocoa powder

This post may contain affiliate links

↓ Jump to Recipe

Remember when you were a kid and someone told you that you couldn't touch the stars? Well, they were wrong. This Buttercream Galaxy Cake brings the entire cosmos right into your kitchen, and trust me—it tastes way better than stardust.

I'll admit, the first time I tried making a galaxy cake, I was a little intimidated. All those swirls and colors? It felt like I needed an art degree just to frost a dessert. But here's the beautiful secret: this cake is actually more forgiving than it looks. Those cosmic swirls? They're supposed to look a little wild and unpredictable. You're creating a galaxy, not a geometry project.

This Buttercream Galaxy Cake has become my go-to showstopper for birthdays, especially when my daughter asked for a "space party" last year. The look on her face when I brought out this cake? That's the kind of kitchen magic I live for.

Jump To Recipe

Why You'll Love This Buttercream Galaxy Cake
What You'll Need
How to Make Your Galaxy Cake
Tips for Galaxy Cake Success
Frequently Asked Questions
Conclusion
Buttercream Galaxy Cake That's Pure Magic

Why You'll Love This Buttercream Galaxy Cake

This isn't just another pretty cake (though it is absolutely gorgeous). The white cake base is incredibly moist thanks to the combination of butter, oil, and sour cream. It's tender without being fragile, and it holds up beautifully under all that dreamy frosting.

The vanilla buttercream is silky smooth and not too sweet—because nobody wants a sugar bomb that makes your teeth hurt. And the galaxy decoration? It's your chance to play with color and texture without worrying about perfection. Every galaxy is different, and yours will be uniquely beautiful.

Plus, this cake feeds a crowd, making it perfect for celebrations when you want to impress without spending your entire weekend in the kitchen.

Galaxy cake with slice removed showing vanilla layers

What You'll Need

The ingredient list might look long, but don't let that scare you off. Most of these are basic baking staples you probably already have. The star players here are good vanilla extract, quality butter, and those gel food colorings—they're essential for getting those deep, vibrant space colors.

The black cocoa powder is your secret weapon for creating depth in your galaxy. Regular cocoa won't give you that true midnight-black color, so it's worth grabbing some online if your local store doesn't carry it.

How to Make Your Galaxy Cake

Baking the Cake

Start by preheating your oven to 350°F and preparing three 8-inch round cake pans. I like to line the bottoms with parchment paper—it's like insurance for getting your cakes out in one piece.

Whisk together your flour, baking powder, and salt in a bowl. In your mixer, cream the butter, oil, and sugar until it's light and fluffy—this usually takes about three minutes. Don't rush this step; you're building structure and incorporating air.

Add your eggs one at a time, mixing well after each addition. Then blend in the sour cream and vanilla. Here's where it gets easy: alternate adding your dry ingredients and milk, starting and ending with the flour mixture. Mix until just combined—overmixing is the enemy of tender cake.

Divide the batter evenly among your pans and bake for 25-30 minutes. They're done when a toothpick comes out clean and the tops spring back when lightly pressed.

Making the Frosting

While your cakes cool completely (patience, I know), make your vanilla frosting. Beat that room-temperature butter until it's pale and creamy, then gradually add the powdered sugar. Finish with vanilla and heavy cream, beating until it's light and fluffy.

This frosting is your base layer—it creates a smooth canvas for your galaxy magic.

Creating the Galaxy Effect

This is where things get fun. Divide your second batch of buttercream into bowls—you'll want portions for pink, purple, blue, deep blue, and black. Start with small amounts of gel coloring and build up; you can always add more but you can't take it away.

Frost your stacked cake with the vanilla buttercream first, getting it as smooth as possible. Then comes the galaxy: dollop your colored buttercreams randomly around the cake. Using an offset spatula or bench scraper, blend the colors together with sweeping motions. You're not trying to mix them completely—you want distinct color patches that flow into each other.

Add small dots of white buttercream for stars, and use your tiny paintbrush to flick white frosting for distant star clusters. The imperfections make it look more realistic.

Tips for Galaxy Cake Success

Room temperature ingredients are crucial—especially your butter, eggs, and sour cream. Cold ingredients won't incorporate properly, and you'll end up with a lumpy batter.

When creating your galaxy effect, work quickly before the buttercream starts to crust. If it does start setting, a quick pass with a warm spatula will soften it up.

Don't stress about making it look exactly like the pictures you've seen online. Real galaxies are messy, beautiful chaos, and so is this cake.

Close-up of galaxy cake slice with three layers

Frequently Asked Questions

Can I make this cake ahead of time?

Absolutely. Bake the cake layers up to two days ahead, wrap them tightly in plastic wrap, and store at room temperature. You can even freeze them for up to three months.

What if I can't find black cocoa powder?

You can use regular cocoa powder mixed with black gel food coloring, but the color won't be quite as deep. Black cocoa is really worth tracking down for the best results.

How long will this cake stay fresh?

Covered at room temperature, it's perfect for 3-4 days. The buttercream actually helps keep the cake moist.

Conclusion

There's something special about serving a cake that makes people gasp before they even taste it. This Buttercream Galaxy Cake delivers that moment every single time. Whether you're celebrating a space enthusiast, impressing dinner guests, or just want to bring a little cosmic wonder to your Tuesday, this cake has you covered. The universe is literally in your hands—or at least on your cake stand. And honestly? That's a pretty sweet place to be.