Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans to prevent sticking.

In a large mixing bowl, cream together the butter and sugar until light and fluffy. This step is crucial for a soft, airy cake texture. Use a hand mixer or stand mixer for the best results!

Add the eggs one at a time, mixing well after each addition. Then stir in the vanilla extract.

In a separate bowl, whisk together the flour, baking powder, and salt.

Gradually add the dry ingredients to the wet ingredients, alternating with the milk, beginning and ending with the dry ingredients. Mix until just combined—overmixing can make the cake dense.

Once your batter is ready, divide it evenly into two bowls.

Add food coloring to one bowl (blue or pink, depending on the gender reveal). Stir gently until the color is fully incorporated. You can add more food coloring if you'd like a deeper shade.

Leave the other bowl of batter as is. This will be your base layer.

Pour the uncolored batter into one of the prepared pans and the colored batter into the other.

Bake both cakes for about 25-30 minutes or until a toothpick inserted in the center comes out clean. You can check them at the 25-minute mark to make sure they don’t overcook.

Once baked, allow the cakes to cool in the pans for 10 minutes, then transfer them to a wire rack to cool completely.

While the cake layers are cooling, prepare the surprise filling!

Once your buttercream frosting is ready, divide it in half. Add food coloring to one half to match the color of the batter you used (pink or blue). The frosting should be thick enough to hold its shape when cut.

Once the cake layers are fully cooled, it’s time to assemble!

Start by placing the first cake layer on a cake stand or plate. Carefully carve out a small circle in the center of the cake using a knife or cookie cutter, creating a hollow space for the surprise filling. Make sure not to cut all the way through the bottom—leave about half an inch of cake around the edges.

Fill the hollowed-out space with the colored buttercream filling. It’s important to be generous with the filling to ensure a dramatic reveal!

Place the second cake layer on top, pressing gently to secure the layers together.

Now it’s time to cover your cake with a beautiful outer layer of frosting. Spread a thin crumb coat of frosting all over the cake to seal in any loose crumbs.

Chill the cake for about 15 minutes to set the crumb coat, then apply a final smooth layer of buttercream. You can use a spatula or piping bag for more decorative touches.

Once the cake is frosted and looking gorgeous, it’s time to reveal the surprise! Carefully cut into the cake and watch your guests’ reactions as they see the color inside. It’s sure to be an unforgettable moment!