Preheat your oven to 350°F (175°C) and line an 8x8-inch baking pan with parchment paper.
Melt the butter in a saucepan or microwave, then stir in the sugar until combined. Let it cool slightly.
Beat in eggs one at a time, then mix in vanilla extract.
Sift together cocoa powder, almond flour, salt, and baking powder in a separate bowl.
Gradually fold the dry ingredients into the wet mixture until just combined. Don’t overmix. It keeps the brownies fudgy.
Fold in chocolate chips or nuts if using.
Pour the batter into the prepared pan and smooth the top.
Bake for 25–30 minutes, or until a toothpick inserted comes out with a few moist crumbs.
Let cool completely before slicing into 12 squares.