Start by preheating your oven to 350°F (175°C). In a large mixing bowl, whip together the granulated sugar and eggs until the mixture becomes light and fluffy, about 5–7 minutes. In a separate bowl, combine your dry ingredients: all-purpose flour, baking powder, baking soda, and salt. In another bowl, whisk together the wet ingredients, including sour cream, vegetable oil, milk, vanilla extract, and champagne, until well blended. Gradually add the dry mixture to the egg mixture, alternating with the wet ingredients.
Once your red and fluffy batter is ready, evenly divide it between two 6-inch cake pans that have been greased and lined with parchment paper. Bake for about 35–40 minutes, or until the cakes are golden and a toothpick inserted in the center comes out clean. Allow the cakes to cool in the pans for about 10 minutes before transferring to a wire rack to cool completely.
While the cake layers are cooling, prepare your strawberry frosting. In a heatproof bowl, whisk together the egg whites and granulated sugar. Place it over a double boiler and gently heat while whisking constantly until the mixture reaches about 160°F (71°C). Transfer the bowl to a stand mixer and whip on high speed until the mixture cools to room temperature and forms stiff peaks, about 7–10 minutes.
With the meringue now at stiff peaks, incorporate the cold butter one cube at a time, mixing on medium speed until fully blended. Increase the mixer speed to high and whip until the frosting is smooth and creamy, taking another 3–5 minutes. Blend in the strawberry puree and food coloring, if using.
Now assemble your Strawberry Champagne Cake. If the cake layers are domed, cut them in half horizontally to make four layers. Place one layer on your serving platter and generously frost the top with strawberry buttercream. Repeat with the other layers. Apply a thin crumb coat around the entire cake and refrigerate for 20 minutes.
Remove the cake from the fridge and apply a thicker layer of strawberry buttercream. Smooth out the frosting for a clean finish, creating swirls or a textured pattern as desired.
Garnish with white and gold sprinkles, fresh strawberries, pomegranate seeds, and any edible flowers. Slice and serve this delightful dessert!
