Prepare cake batter according to package directions. Pour into two greased and floured 9-inch heart-shaped baking pans. Bake at 350 degrees for 30–33 minutes or until a toothpick inserted near the centers comes out clean. Cool for 10 minutes before removing from pans to wire racks to cool completely.
In a large bowl, combine yogurt and confectioners' sugar; fold in whipped topping. Split each cake into two horizontal layers. Place one bottom layer on a serving plate; top with a fourth of the yogurt mixture. Repeat layers three times..
Spread the raspberry pie filling over the top of the cake to within 1 inch of the edges. Cover and refrigerate until serving