
1 tsp baking powder
½ tsp baking soda
¼ tsp salt
½ cup unsalted butter, softened
¾ cup granulated sugar
2 large eggs
1 tsp vanilla extract
½ cup buttermilk
1 cup unsalted butter (for frosting)
3 cups powdered sugar
2–3 tbsp heavy cream
1 tsp vanilla extract
Blue gel food coloring
1 tsp cocoa powder
1–2 tsp water or vanilla extract