Step 1

Preheat oven to 375°F. Spray a 9-inch cast iron skillet or cake pan with non-stick cooking spray.

Step 2

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

Step 3

In a large bowl with an electric mixer on medium speed, combine sugar and butter or shortening and mix until light and fluffy, about 3 minutes. Add egg and vanilla, mixing until thoroughly combined. Reduce mixer speed to low and alternating adding the dry ingredients and the milk to the sugar mixture, beginning and ending with the dry ingredients, mixing until just combined after each addition. Fold in blueberries. Spoon batter into prepared pan.

Step 4

Make the Streusel Topping: In a medium bowl, combine flour, brown sugar, cinnamon and salt. With your hands, work in butter pieces until small clumps form. Spread topping evenly over batter.

Step 5

Bake in preheated oven for 40-45 minutes.