Preheat your oven to 375°F. Prepare your baking pan by lining it with parchment paper.

Combine the dry ingredients: 2 cups flour, 2 tsp baking powder, and 1/2 tsp salt. Whisk until mixed.

Cream together 1/2 cup softened butter and 3/4 cup granulated sugar until light and fluffy, about 3-5 minutes.

Add 2 large eggs, 1/2 cup sour cream, and 2 tsp vanilla extract to the butter mixture, mixing to a smooth batter.

Fold the dry mixture into the wet batter until just combined.

Gently fold in 1 1/2 cups fresh blueberries.

Prepare the streusel topping: Mix 1/2 cup flour, 6 tbsp brown sugar, 1 tsp cinnamon, and 1/4 tsp salt, then work in 1/4 cup cold butter until crumbly.

Pour the batter into the prepared pan and sprinkle streusel topping on top.

Bake for 42-48 minutes or until a toothpick inserted comes out clean.

Cool for 30 minutes in the pan before transferring to a wire rack.