1. Prepare the cake pans

• Preheat oven to 175°C (350°F).
• Grease two 9-inch round cake pans and line the bottoms with parchment paper. Lightly flour the sides and tap out any excess.

2. Mix dry ingredients

• In a medium bowl, whisk together flour, baking powder, and salt. Set aside.

3. Cream the butter and sugar

• In a large mixing bowl, beat softened butter and granulated sugar with a hand or stand mixer until light and fluffy, about 3–4 minutes.
• Scrape down the sides of the bowl as needed for even mixing.

4. Add eggs and vanilla

• Add eggs one at a time, beating well after each addition.
• Mix in vanilla extract until fully combined.

5. Add dry ingredients and liquids

• Add half of the dry ingredients to the batter and mix on low speed.
• Pour in the milk and add the yogurt or sour cream. Mix gently.
• Add the remaining dry ingredients and mix just until incorporated—avoid overmixing.

6. Bake the cake

• Divide the batter evenly between the prepared pans and smooth the tops.
• Bake for 30–35 minutes, or until a toothpick inserted in the center comes out clean.
• Let cakes cool in the pans for 10 minutes, then turn out onto wire racks to cool completely.

7. Make the buttercream frosting

• In a large bowl, beat softened butter until creamy and pale.
• Gradually add powdered sugar, beating on low at first, then increasing speed as it incorporates.
• Add vanilla extract, a pinch of salt, and milk as needed to reach a smooth, spreadable consistency.

8. Assemble and decorate

• Level the cake layers if needed. Place one layer on a cake stand and spread frosting on top.
• Add the second layer and frost the top and sides of the cake.
• Decorate as desired with piped rosettes, sprinkles, fresh flowers, or fruit.