Blackberry Layered Cake with Lime

My friend recommended this recipe from Baked Perfection. Although the recipe is for cupcakes, she adapted it for a layered cake. As she suggested, I alternated blackberry filling and blackberry frosting layers. The recipes below include my adaptations but use the link above for the original recipe.

1 cup salted butter, softened
2 cups sugar
3 eggs
2 tsp vanilla extract
4 tbsp fresh lime juice
zest from 2 limes (use more if desired!)
3 1/2 cups flour
1 tsp baking soda
1/2 tsp baking powder
1/2 tsp salt 
2 cups sour cream

Cream butter and sugar. Add eggs, vanilla, and lime. In a separate bowl, combine dry ingredients. Add dry ingredients to mixture alternating with the sour cream. Pour batter into three round greased cake pans. Bake for 25 to 30 minutes at 350° or until golden brown and edges begin to pull away from the side. Cool completely before frosting. Decorate with fresh fruit, homemade blackberry syrup, or chocolate sauce.

Blackberry Filling

16 oz. frozen blackberries

8 oz. frozen raspberries

1-2 tsp lemon juice concentrate

3 tbsp cornstarch

Heat berries and lemon juice in a saucepan until they form a liquid substance. Add cornstarch, mix well. Bring to a boil and stir until mixture begins to thicken. Remove from heat and cool completely. 

Blackberry Frosting

1 cup butter, softened (I used light butter, salted)

1 tsp vanilla

pinch of salt

1/3 cup blackberry filling

6 cups powdered sugar

Cream butter until smooth. Add vanilla, salt, and blackberry filling. Gradually add powdered sugar until frosting reaches a desired consistency. Keep in refrigerator until ready to use.