Preheat oven to 350°F (175°C). Grease and line cake pans.
Whisk dry ingredients: Flour, baking powder, and salt in a bowl.
Cream butter & sugar: Beat until fluffy (~3 mins). Add eggs one at a time, then vanilla.
Alternate mixes: Add dry ingredients and milk in batches, mixing until just combined.
Bake: Divide batter into pans. Bake for 22-25 mins or until a toothpick comes out clean. Cool completely.
Beat butter until smooth. Gradually add powdered sugar, cream, and vanilla. Whip until light.
Fold in half the berries (reserve some for garnish).
Layer cakes with frosting in between. Cover the entire cake with remaining frosting.
Decorate with fresh berries. Chill for 30 mins before serving.