Preheat oven to 350 degrees F (175 degrees C). Grease and flour an 8-inch square pan.
In a large saucepan, melt 1/2 cup butter. Remove from heat, and stir in sugar, eggs, and 1 teaspoon vanilla. Beat in 1/3 cup cocoa, 1/2 cup flour, salt, and baking powder. Spread batter into prepared pan.
Sprinkle bacon over the top of the batter.
Bake in preheated oven for 25 to 30 minutes. Do not overcook.