Preheat your oven to 350°F (175°C).

Grease your 9x9 inch baking pan or line it with parchment paper.

In a mixing bowl, combine the melted butter and granulated sugar. Whisk until smooth and creamy.

Add the eggs and vanilla extract to the bowl, and mix until fully incorporated.

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

Gradually add the dry mixture to the wet ingredients, stirring until just combined.

Pour the brownie batter into your prepared baking pan, spreading it evenly.

Bake in the preheated oven for 20 to 25 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs.

Allow the brownies to cool in the pan for at least 10 minutes before slicing.