Preheat the oven to 350°F (175°C). Line an 8x8-inch baking pan with parchment paper or lightly grease it.

In a large bowl, whisk together the melted butter and sugar until well combined. Add the eggs and vanilla extract, then whisk until smooth.

In a separate bowl, mix the flour, cocoa powder, salt, and baking powder.

Add the dry ingredients to the wet ingredients and stir just until combined. Do not overmix.

Toss the fresh blueberries with the 2 tablespoons of flour to help prevent them from sinking, then gently fold them into the batter.

Spread the batter evenly into the prepared pan.

Bake for 28 to 32 minutes, or until a toothpick inserted near the center comes out with a few moist crumbs.

Let the brownies cool completely in the pan before slicing. Dust with powdered sugar if desired.