In a bowl, sift together flour, baking powder, baking soda and salt.
In the bowl of an electric stand mixer fitted with the paddle attachment, beat butter until creamy - about 1 minute.
Add the sugar, then add eggs one at a time. The mixture may separate, but it will come together when flour is added. Add vanilla.
Gradually beat in ⅓ of flour mixture just until blended, then ½ of buttermilk, scraping down sides of bowl if needed. Repeat additions, ending with flour mixture. Beat just until blended.
Fold in cherries and confetti. Divide batter between pans, weighing each to ensure even distribution.
Bake in centre of oven until a cake tester inserted in centre of cakes comes out clean, approximately 30 min.
Remove pans to a rack. Cool 15 min, then remove cakes to a rack to cool completely before frosting.
To make the Frosting/Filling:
In the bowl of an electric mixer fitted with the paddle attachment, whip butter for 5 minutes on medium speed until pale & creamy.
Add remaining ingredients, except the cherries, and mix on low speed for 1 minute, then on medium speed for 6 minutes. Fold in cherries.
Notes
[cake recipe from Chatelaine.com /frosting recipe from Sweetapolita.com]