Preheat the oven to 350°F (175°C).

Grease a 9x9 inch baking dish with butter or cooking spray.

In a mixing bowl, combine the sugar, cocoa powder, flour, salt, and baking powder.

In another bowl, whisk together the melted butter, vanilla extract, and eggs until well blended.

Gradually add the wet mixture to the dry ingredients, stirring until just combined.

Slowly incorporate the milk into the batter and mix until smooth.

Pour the batter into the prepared baking dish and spread it evenly.

Bake in the preheated oven for 30 minutes or until the edges are set but the center remains soft.