Blueberry Crumble Coffee Cake

A delicious refreshing dessert! All you for the crumble topping is: 1/2 cup brown sugar, 1/2 cup flour, 1/2 teaspoon cinnamon, 1/2 teaspoon nutmeg, 1/4 teaspoon cardamom, 1/4 cup butter, softened. For the cake: 2 cups flour, 2 teaspoons baking powder, 1/4 teaspoon salt, 1/2 teaspoon cinnamon, 3/4 cup sugar, 1/4 cup butter, softened, 1 large egg, 1 teaspoon vanilla extract, 1/2 cup buttermilk, 3 cups fresh blueberries.

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Source : http://sweetannas.com/2010/07/blueberry-crumble-coffee-cake.html