Step 1: Bake the Cake Layers

1. Preheat the oven to 350°F (175°C). Grease and line three 8-inch round cake pans or one dome-shaped pan.
2. In a medium bowl, whisk together flour, baking powder, and salt. Set aside.
3. In a large mixing bowl, beat butter and sugar until light and fluffy (about 3-4 minutes).
4. Add eggs one at a time, mixing well after each addition. Stir in vanilla extract.
5. Alternate adding dry ingredients and milk/sour cream mixture, beginning and ending with dry ingredients. Mix until just combined.
6. Pour the batter evenly into the prepared pans and bake for 30–35 minutes, or until a toothpick inserted in the center comes out clean.
7. Let cakes cool in the pans for 10 minutes, then transfer to a wire rack to cool completely.

Step 2: Prepare the Buttercream Frosting

1. Beat butter until creamy and smooth. Gradually add powdered sugar, mixing on low speed.
2. Stir in vanilla extract and heavy cream, then beat for 2–3 minutes until light and fluffy.
3. Divide and tint the frosting with pink food coloring as desired.

Step 3: Assemble the Barbie Cake

1. Stack the cooled cake layers with frosting in between. If using round cakes, carve the layers into a dress shape.
2. Cut a hole in the center of the cake and insert the Barbie doll (wrapped in plastic wrap).
3. Apply a crumb coat (thin frosting layer) and chill for 20 minutes.

Step 4: Decorate the Dress

1. Use a star piping tip to create rosettes or ruffles on the cake dress.
2. Add edible pearls, glitter, or fondant details for extra elegance.
3. Chill the cake for at least 30 minutes before serving.