Here's the recipe that I used for the filling:
1 1/2 cups frozen raspberries
1 1/2 tablespoons cornstarch
2 tablespoons fresh lemon juice
1/4 cup sugar
In a saucepan, combine all ingredients and bring to a boil over medium-high heat. Use a wire sieve to remove the raspberry seeds. Once the filling has cooled completely, spread on to cake.
I topped the cake with chocolate frosting and sprinkles.