Preheat the oven to 350°F (175°C). Grease and line two 8-inch round cake pans with parchment paper.

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

In a large bowl, beat the butter and sugar together until light and fluffy, about 3 to 4 minutes.

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

In a small bowl, whisk together the milk and sour cream.

Add the dry ingredients to the butter mixture in three parts, alternating with the milk mixture, beginning and ending with the dry ingredients. Mix just until combined.

Divide the batter evenly between the prepared pans and smooth the tops.

Bake for 28 to 32 minutes, or until a toothpick inserted into the center comes out clean.

Cool the cakes in the pans for 10 minutes, then turn them out onto a wire rack to cool completely.

Tint portions of the buttercream with blue, gold, and white gel food coloring to create a Virgo-inspired color palette.

Place one cake layer on a serving plate and spread a layer of frosting on top. Add the second layer and frost the top and sides of the cake smoothly.

Decorate with swirls or simple piping in the Virgo theme colors, then finish with edible silver stars, pearl sprinkles, and a Virgo topper or symbol.

Chill the cake for 20 to 30 minutes before slicing for cleaner cuts.