Preheat your oven to 350°F (175°C) and grease your 9x13 inch baking pan or line it with parchment paper.
In a microwave-safe bowl, melt the butter in 30-second increments until it's completely melted.
In a separate mixing bowl, combine the sugar and cocoa powder.
Pour the melted butter over the sugar and cocoa mixture and stir until well combined.
Add the eggs one at a time, mixing well after each addition.
Stir in the vanilla extract.In another bowl, whisk together the flour, baking powder, and salt.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Be careful not to overmix.
Pour the batter into your prepared baking pan, spreading it evenly.
Bake in the preheated oven for 25-30 minutes or until a toothpick inserted into the center comes out with a few moist crumbs.
Allow the brownies to cool in the pan for about 15 minutes before cutting them into squares.