Prepare the raspberry filling by combining fresh raspberries, sugar, and lemon juice in a saucepan. Cook for 10-15 minutes until thickened. Chill for 30 minutes.
Preheat the oven to 350°F (175°C) and prepare two 8-inch round cake pans with parchment paper.
In one bowl, sift flour, baking powder, baking soda, and salt. In another bowl, cream butter and oil with sugar and vanilla until fluffy. Add egg and egg whites, then incorporate sour cream. Mix in dry ingredients and milk, then fold in raspberries.
Divide batter between cake pans. Bake for 25-30 minutes until golden and toothpick comes out clean. Cool in pans for 20-30 minutes, then invert onto wire racks.
Prepare the ganache frosting by chopping white chocolate. Heat heavy cream to a simmer, pour over chocolate, let sit, then whisk until smooth. Chill overnight and beat until fluffy.
Assemble the cake by layering with frosting and raspberry filling, then cover with ganache and garnish with raspberries.
Ensure the chocolate is finely chopped for smoother ganache preparation.