Line an 8x8 or 9x9 inch square metal pan with parchment paper and set aside. Preheat the oven to 350℉.
Make the almond streusel. In a medium-sized bowl, add softened butter, brown sugar, white sugars, almond extract, and flour. Mix using your hands or a fork until a crumble forms. Add in slivered almonds and then mix a few more times. Set aside.
1 1/3 cups all-purpose flour, 1/3 cup dark brown sugar, 1/4 cup white sugar, 1/2 cup butter, 1/3 cup slivered almonds, 1/2 tsp almond extract
In a medium-sized bowl, add flour, baking soda, baking powder, and salt. Stir to combine and set aside.
2 cups all-purpose flour, 1 tsp baking powder, 1/2 tsp baking soda, 1/4 tsp salt
In a large bowl, whisk melted and cooled butter, milk, eggs, and sour cream until smooth.
3/4 cups butter, 1/4 cup milk, 2 eggs, 1 cup sour cream*
Add in brown and white sugar and continue on whisking.
1/2 cup white sugar, 1/2 cup dark brown sugar
Add in dry ingredients. Using a spatula, gently fold until a soft batter forms. Do not overmix!!!
Make the blackberry layer. In a medium-sized bowl, add fresh blackberries, lemon juice, lemon zest, white sugar, and flour. Mix until well combined.
2 cups blackberries, 2 tbsp lemon juice, Zest of 1 large lemon, 1/2 tsp almond extract, 3 tbsp white sugar, 2 tbsp all-purpose flour
Layer. Transfer the cake batter into the prepared pan and spread evenly.
Take the blackberries and distribute them evenly on top of the cake batter. Sprinkle the almond streusel on top.
Bake for 45-55 minutes or until a toothpick comes out clean. Mine took 42 minutes exactly!
Cool completely, slice, and enjoy!