Preheat oven to 350º. Put a long piece of non-stick foil in the bottom of a 9 x 9 inch pan, fitting so it covers the bottom of pan, the two shorter sides, plus has some overhang on each side for easy removal.

In a large microwave safe bowl, melt the 1 cup butter in the microwave.

Stir in sugar, then eggs and vanilla.

Add cocoa powder, salt and baking powder.

Stir in flour and mix till just combined.

Spread evenly into pan.

Bake for about 35 minutes. (check a few mins before and keep checking if not done)

Cool completely.

Cut.