Preheat oven to 350°F and prepare an 8x8 baking pan by lining it with parchment paper. I like to spray with cooking spray after it’s lined.

For the topping: In a medium bowl, mix the brown sugar, flour, cardamom, and cinnamon. Add the 1/4 cup of butter into the dry mixture and using your fingers, mix until it's crumbly. Place the streusel in the freezer while you mix the cake batter.

For the blackberry coffee cake: Using a stand mixer or a hand-held mixer, cream together the 6 Tbsp butter and granulated sugar for 2-3 minutes, until light and fluffy.

Add the eggs one at a time. Scrape up and down the bowl once, if needed to fully combine the first egg and add the vanilla extract and the almond extract and beat on medium until well blended. Next, add the sour cream and beat on medium until combined, about 30-60 seconds.

Pour about half the flour into the wet ingredients, then add the cornstarch, baking powder, kosher salt, and remaining flour. Mix on low until combined. Use a spatula to finish mixing until just combined. The batter will be nice and thick.

Spread about half the batter into the bottom of the prepared pan. Top with half of the cold streusel mixture and the blackberries. Add the remaining batter in spoonful’s on top of the blackberries and spread evenly if you can. Then top with remaining streusel.

Bake for 30-35 minutes. Allow to cool in the pan set on a wire cooling rack.