1. In a bowl, combine ½ cup flour, ⅓ cup sugar, and ¼ teaspoon cinnamon. Cut in cold butter until the mixture is crumbly. Chill while making the batter.

2. In a large mixing bowl, cream softened butter with ¾ cup sugar until light and fluffy.

3. Add eggs one at a time, beating well after each. Mix in vanilla extract.

4. In a separate bowl, whisk together 1 ½ cups flour, baking powder, and salt.

5. Add the dry ingredients to the wet mixture in batches, alternating with the milk, beginning and ending with the flour mixture. Stir until just combined.

6. Toss the blueberries with ¼ teaspoon flour and gently fold them into the batter.

7. Pour batter into a greased 9×9-inch pan and spread evenly.

8. Sprinkle the chilled crumb topping over the batter.

9. Bake at 350°F (175°C) for 40–45 minutes or until a toothpick inserted in the center comes out clean.

10. Let cool for 10–15 minutes before slicing and serving.