Preheat the oven to 350°F (175°C) and grease a heart-shaped baking pan.

Melt the butter in a microwave-safe bowl until liquid.

In a mixing bowl, combine melted butter with both sugars until smooth. Add eggs one at a time, mixing well after each addition, followed by the vanilla extract.

In another bowl, whisk together the flour, cocoa powder, baking powder, and salt. Gradually add the dry ingredients to the wet mixture until combined.

Pour the batter into the prepared pan and spread evenly. Bake for 25-30 minutes or until a toothpick inserted comes out clean.

Let cool for 10 minutes before transferring to a wire rack. Once completely cooled, use a heart-shaped cutter to cut out shapes.