Preheat your oven to 350°F (175°C). Grease a 9x9 inch baking pan.
In a mixing bowl, combine melted butter and sugar. Add eggs one at a time, beating well after each addition. Stir in coffee liqueur.
In another bowl, whisk together cocoa powder, flour, salt, and baking powder. Gradually add dry ingredients to the wet mixture, stirring until just combined.
Pour the batter into the prepared baking pan and spread evenly. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
Allow the brownies to cool in the pan before cutting into squares. Enjoy!