Preheat your oven to 350°F (175°C). Grease a 9x9-inch baking pan or line it with parchment paper.

Combine the melted butter and granulated sugar in a medium bowl. Stir until smooth.

Add the eggs and vanilla extract. Mix until well incorporated and creamy.

Whisk together the cocoa powder, flour, salt, and baking powder in a separate bowl.

Gradually mix the dry ingredients into the wet ingredients, stirring gently until just combined.

Pour the brownie batter into the prepared baking pan and spread it evenly.

Bake in the preheated oven for 20–25 minutes. Check with a toothpick; they are ready when a few moist crumbs stick.

Cool the brownies in the pan for about 10–15 minutes, then transfer them to a wire rack to cool completely.

Cut into squares once cooled and serve.