Okay, I had to look this up---no such fruit in my area, although they look similar to blackberries---which are sweet when ripe. I also saw ideas for jams and liquors.
Cloudberry Layer Cake
Ingredients
Makes 16 servings
6 large eggs (about 1 1/3 cups), room temperature
1 1/3 cups granulated sugar
1 teaspoon pure vanilla extract
1/8 teaspoonkosher salt
1 1/3 cups all-purpose flour, stirred before measuring
2 cups cloudberry preserves
3 cups heavy cream, whipped
1/4 cup confectioners' sugar
2 teaspoons pure vanilla extract
1/2 cup dark rum
Directions
Preheat oven to 350 degrees. Line two 9-inch round cake pans with parchment paper. Break eggs into a liquid 2-cup measuring cup to measure.
In the bowl of an electric mixer fitted with the whisk attachment, combine eggs and sugar, beating on high speed until light and lemon colored, about 5 minutes.
Beat in vanilla and salt. With a rubber spatula, thoroughly fold in flour.
Divide batter evenly between the two pans. Bake until the cake springs back when touched in the center, 25 to 30 minutes. Transfer cakes to a wire rack to cool. Loosen edges of cooled cakes and remove from pans. Using a serrated knife, slice cakes horizontally to make four cake layers in all.
For the filling: Whip the cream until firm but not stiff, and add the confectioners' sugar and vanilla.
To assemble the cake: Place bottom layer on cake plate, brush cake with rum, and spread with one-third of the filling. Top with the second layer, brush with rum, and spread with 1/2 of the preserves. Top with the third layer, brush with rum, and spread with one-third of the filling. Top with the fourth layer, brush with rum, and spread with remaining preserves. Using a 12-inch pastry bag fitted with a 1/2-inch star tip, pipe remaining filling on cake in a decorative pattern.