This fruit-filled creation is perfect for a springtime affair.
Preheat oven to 350 degrees. Coat cake pans with cooking spray; cover bottoms with parchment, and coat again; set aside. Sift together flour, baking powder, salt, and baking soda in a large bowl; set aside.
Put butter and sugar into the bowl of an electric mixer fitted with the paddle attachment; mix on medium speed until fluffy, about 12 minutes. Mix in vanilla. Add eggs, 1 at a time, mixing well after each addition. Add flour mixture in 2 batches, alternating with the buttermilk. Divide batter among prepared pans. Gently toss berries in flour to coat completely, and gently press into batter.
Bake until a cake tester inserted in centers comes out clean. (If the cakes become too dark while baking, cover with foil.) Transfer to wire racks; let cool in pans slightly. Invert cakes onto racks. Remove parchment, and reinvert.
To assemble: each cake in half horizontally, making 4 layers of each size. Spread buttercream on 3 cake layers (see note below for amounts). Stack layers, placing the plain layer on top. Coat tiers with buttercream; chill. Smooth fondant over tiers.
Note: Make this batter recipe once for a 3-tiered cake to serve 70. Bake 2 cakes for each tier; cut each into 2 layers.
Batter amounts and cooking times for 3-inch-deep round pans: 6-inch: 2 cups batter with 15 berries per cake (4 cups, 30 berries total), 40 minutes; 8-inch: 3 cups batter with 25 berries per cake (6 cups, 50 berries total), 40 minutes; 10-inch: 4 cups batter with 35 berries per cake (8 cups, 70 berries total), 40 minutes.
Filling, frosting, and fondant amounts for each tier: 6-inch: 1/2 cup buttercream per layer, 1 1/2 cups buttercream for exterior (3 cups total), 1 1/2 pounds fondant; 8-inch: 1 cup buttercream per layer, 2 cups buttercream for exterior (5 cups total), 2 pounds fondant; 10-inch: 1 1/2 cup buttercream per layer, 3 cups buttercream for exterior (7 1/2 cups total), 2 1/2 pounds fondant.