Use a vanilla (e.g., using whole eggs, or just whites) recipe for the cake, and use pastry cream mixed with chopped fresh berries for the filling.
Use a buttercream for cake assembly; you want to make a ring or dam at the outside edge of the cake with the buttercream in order to hold the softer pastry cream filling in and prevent it from oozing out the sides and shifting the cake. I like to sprinkle the chopped fruit on the cake layer before spreading the pastry cream on; it helps to control where the fruit goes. You can use two layers of cake and a single layer of filling or if you bake in 2” pans you can split horizontally each cake into 2 (so you’d end up with 4 layers) and build a cake from three layers of cake and two layers of filling. Crumb coat the assembled cake with buttercream. (When the cake is chilled, the buttercream is firm and helps to hold things together). You can use whipped cream for the outside if you want; it’s easier to use buttercream to pipe a basketweave pattern though.