Preheat the oven to 350°F. Grease and flour three 8-inch round cake pans.

In a medium bowl, whisk together flour, baking powder, and salt. Set aside.

In a large bowl, beat the softened butter and granulated sugar until light and fluffy. Add the eggs one at a time, mixing well after each addition. Stir in the vanilla and melted white chocolate.

Gradually add the flour mixture alternately with the milk, starting and ending with the flour. Mix until just combined.

Divide the batter evenly between the prepared pans. Bake for 25–30 minutes or until a toothpick inserted comes out clean. Let the cakes cool in the pans for 10 minutes before transferring to wire racks to cool completely.

For the raspberry filling, combine the raspberries, sugar, and lemon juice in a saucepan. Cook over medium heat until the berries break down.

Add the cornstarch mixture and stir until thickened. Let it cool completely.

For the frosting, beat the softened butter until creamy. Gradually add the powdered sugar. Stir in the melted white chocolate, vanilla, and enough milk to reach your desired consistency.

To assemble the cake, level the cakes if necessary. Place the first layer on a cake board. Spread a thin layer of frosting, followed by a layer of raspberry filling. Repeat with the next layer.

Frost the outside and top of the cake. Chill slightly to set. Decorate with fresh raspberries, white chocolate curls, or piped swirls of frosting.