Recipe

Make Batter

1. Preheat oven to 325°F. Grease cake pans and line bottoms with parchment paper.
2. In bowl, combine flour, baking powder, baking soda and salt, and stir with fork to blend.
3. In separate bowl, using electric mixer, beat butter and sugar until light and fluffy. Add eggs one at a time, beating well between additions. Add vanilla paste and beat until incorporated.
4. Add a third of the dry ingredients to the batter, beating until combined. Add half the buttermilk. Repeat, alternating ingredients, until all dry ingredients and buttermilk are incorporated.

Make Icing

1. In bowl of stand mixer, combine egg whites and sugar.
2. Pour water to depth of 1-inch in pot, place on stovetop and bring water to simmer. Rest mixing bowl in pot (it should fit without water touching bottom of bowl, creating a double boiler effect).
3. Whisk mixture until sugar has fully dissolved and temperature on instant-read thermometer reads 160°F (this will pasteurize the egg whites). Whisk in vanilla and salt.
4. Reattach bowl to stand mixer. Using whisk attachment, beat mixture on high until meringue holds stiff peaks and both it and bowl have returned to room temperature, about 20 minutes.
5. Switch to beater attachment and add butter one cube at a time, beating well after each addition. When all butter is incorporated, turn mixer to medium-high and beat 2 minutes longer, or until silky smooth. Use immediately or chill slightly if needed before using.

Layer, Ice and Decorate Cake

1. Trim domed tops from cake layers and place 1 layer, cut-side up, on cake board on rotating cake stand.
2. Using piping bag with plain round icing tip, pipe thin line of icing around inside edge, then, with offset spatula, spread about 1⁄2 cup icing evenly on top of first layer. Add next layer and repeat until there are 3 layers. Lightly frost top and sides of cake. Remove from stand and refrigerate for at least 10 minutes, or until icing has firmed.
3. Replace cake on stand and apply another layer of icing as base layer.
4. Divide remaining icing between 3 or more bowls and tint with colors of your choice. Transfer to piping bags fitted with #233 icing tip and, starting with bottom of cake, pipe on different colors to create shag rug effect.