In a medium saucepan, combine 1 1/2 cups of blackberries, 2 tablespoons of sugar, and a splash of water. Cook over medium heat for about 10 minutes, stirring occasionally, until thickened. Strain and cool before using.

Preheat your oven to 350°F (175°C). Prepare two 8-inch round cake pans by greasing, lining with parchment paper, and dusting with flour.

In a large bowl, whisk together 2 1/2 cups of flour, 2 tsp baking powder, 1/2 tsp baking soda, and 1/2 tsp salt.

In another bowl, beat 1 cup of butter and 1 3/4 cups of sugar on medium speed until light and fluffy, about 3-4 minutes.

Add 3 eggs, one at a time, mixing well after each. Stir in 2 tsp vanilla extract and 1 tsp lemon zest.

Combine 1 cup of buttermilk and the cooled blackberry puree, mix, then gradually add to the flour mixture, alternating with buttermilk.

Divide the batter between the pans and bake for 28-32 minutes, or until a toothpick comes out clean.

Let the cakes cool in the pans for 10 minutes, then turn out onto wire racks to cool completely.

Beat together 4 oz cream cheese and 1 cup butter until creamy, then gradually add 3 1/2 cups powdered sugar and 1/3 cup blackberry puree.

Once cooled, frost the first layer, add the second layer, and frost the top and sides. Decorate as desired.