Directions:

Preheat your oven to 375 degrees F. Prepare a 9-inch square cake pan or springform pan with cooking spray. Line the bottom of the prepared baking pan with parchment paper and set aside.

Make the streusel topping first. In a small bowl, combine the light brown sugar, flour, cinnamon, nutmeg, cardamom, and softened unsalted butter. Mix with a fork or pastry cutter until small crumbs form. Refrigerate while you make the batter.

In a large mixing bowl, whisk together the dry ingredients for the cake: flour, baking powder, salt, and cinnamon.

In another large bowl, cream together the unsalted butter and sugar until smooth. Blend in the egg and vanilla. Add the flour mixture and buttermilk alternately, beginning and ending with the flour — flour, buttermilk, flour, buttermilk, flour. Fold in the blueberries carefully, keeping the berries as whole as possible.

Spread the batter into the prepared pan. Scatter the chilled crumb topping evenly over the top of the blueberries, pressing gently so it makes contact.

Bake for 50 to 60 minutes, until a cake tester or toothpick inserted in the center of the cake comes out clean and the crumble looks golden brown. If the top is browning too quickly, tent loosely with foil for the last ten minutes. Cool completely before slicing.