Simmer the Blackberry Reduction: Combine 1 cup of fresh blackberries, ¼ cup granulated sugar, and ¼ cup water over medium heat for 8-10 minutes, crush and strain, then cool.

Prepare Cake Pans: Preheat oven to 350°F (175°C), grease two 8-inch pans, and line the bottoms with parchment paper.

Mix Dry Ingredients: In a bowl, whisk together 2 ¾ cups all-purpose flour, 2 teaspoons baking powder, 1 teaspoon baking soda, and ½ teaspoon salt.

Cream Butter and Sugar: Beat 1 cup unsalted butter and 2 cups granulated sugar until light and fluffy, add 4 eggs one at a time, and mix in 2 teaspoons vanilla and lemon zest.

Combine Wet Ingredients: In another bowl, whisk 1 cup buttermilk with the cooled blackberry reduction.

Combine Ingredients: Gradually add the dry ingredients to the butter mixture, alternating with the buttermilk mixture, until just combined.

Bake the Cake: Divide batter between pans and bake for 28-32 minutes until a toothpick comes out clean, then cool for 10 minutes in pans.

Prepare Frosting: Beat 8 oz cream cheese and ½ cup unsalted butter until smooth, then add 4 cups powdered sugar and ¼ cup blackberry reduction.

Assemble Cake: Place one layer on a plate, spread frosting, add the second layer, and frost the top and sides, garnishing as desired.