Simple Blueberry Coffee Cake for 12

Instructions:

1. Preheat the oven to 350°F (175°C). Grease a 9x9 inch baking pan with butter or line it with parchment paper.
2. In a small bowl, combine 1/2 cup flour, brown sugar, and cinnamon. Rub the cold cubed butter into the mixture with a fork or fingers until pea-sized crumbs form. Set aside.
3. Gently toss the fresh blueberries with one tablespoon of flour to prevent them from sinking.
4. In a large bowl, beat the softened butter and granulated sugar on medium-high until light and fluffy (about 3 minutes).
5. Beat in the eggs one at a time, then stir in the vanilla extract and sour cream until smooth.
6. Alternately add the flour mixture (flour, baking powder, salt) and the milk to the butter mixture, starting and ending with the flour. Mix on low speed just until combined.
7. Using a rubber spatula, gently fold in the floured blueberries by hand.
8. Pour the batter into the prepared pan and smooth the top with a spatula.
9. Sprinkle the cinnamon streusel evenly over the surface, pressing very lightly.
10. Bake for 40 to 45 minutes until the edges are golden brown and a toothpick inserted into the center comes out clean.
11. Let the cake cool in the pan for 20 minutes before slicing.