Preheat your oven to 350°F (175°C) and grease and flour two 9-inch round cake pans.

In a small bowl, mash 1 1/2 cups of blackberries with a fork until juicy but slightly chunky. Set aside.

In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.

In a large bowl, cream the butter and granulated sugar together until light and fluffy, approximately 3-5 minutes.

Add the eggs one at a time, beating well after each addition.

Mix in the vanilla extract, optional lemon zest, and purple food coloring until combined.

Gradually add the dry ingredients and buttermilk, starting and ending with dry ingredients. Mix until just combined.

Gently fold in the mashed blackberries until evenly distributed.

Divide the batter between the prepared pans, smoothing the tops.

Bake for 30-35 minutes, or until a toothpick comes out clean.

Allow the cakes to cool in the pans for 10 minutes. Then turn them out onto wire racks to cool completely.

For the frosting, reduce 1 cup of fresh blackberries over low heat until thick, then strain and let cool.

Beat the butter and cream cheese together until smooth and creamy.

Gradually add powdered sugar, mixing on low speed until incorporated and smooth.

Mix in blackberry puree, vanilla extract, and salt until well combined.

Place one cake layer on a serving platter, spread frosting over the top, add the second cake layer, and cover the whole cake with remaining frosting.

Garnish with extra blackberries, edible flowers, and mint leaves as desired.