Make the Raspberry Swirl:
In a small saucepan, combine raspberries, sugar, and lemon juice. Cook over medium heat until berries break down. Stir in cornstarch slurry and cook for another 1–2 minutes until thickened. Let cool completely.

Make the Cake:
Preheat oven to 350°F (175°C). Grease and flour two 8-inch round cake pans.
In a bowl, whisk together flour, baking powder, and salt.
In a large bowl, cream butter and sugar until light and fluffy. Add egg whites and vanilla, mixing well.
Mix in the flour mixture alternately with coconut milk and sour cream until just combined.
Divide batter evenly into pans. Drop spoonfuls of raspberry sauce into each and gently swirl with a knife.
Bake 25–30 minutes, or until a toothpick comes out clean. Cool completely.

Make the Frosting:
Beat butter until smooth. Add powdered sugar, one cup at a time. Add coconut milk, vanilla, and salt. Beat until fluffy.

Assemble the Cake:
Level cakes if needed. Place one layer on a plate, top with frosting, then the second layer. Frost the whole cake.
Press shredded coconut all over the cake, covering it completely to resemble a snowball. Chill until ready to serve.