Preheat your oven to 350°F (175°C) and grease and flour an 8x8 inch baking pan. This ensures the brownies won't stick and will cook evenly.

In a medium bowl, whisk together the flour, cocoa powder, baking powder, and salt. Set this aside for later.

In a large bowl, combine the melted butter and granulated sugar, mixing until smooth. Beat in the eggs one at a time, then stir in the vanilla extract.

Gradually add the dry ingredient mixture to the wet ingredients, mixing until just combined. Fold in any optional chocolate chips or nuts at this stage.

Pour the batter into the prepared baking pan and spread it evenly. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out with moist crumbs, not wet batter.

Allow the brownies to cool completely in the pan on a wire rack before cutting them into squares. This prevents crumbling and ensures clean slices.