Preheat oven to 350 degrees. Line an 8x8- (for more cake-like brownies) or 9x9-inch (for more dense brownies) square pan with foil or parchment paper, leaving extra for "handles."
Put all ingredients into a bowl and stir by hand until smooth (about 30 seconds). Spread batter in pan and bake for about 20 minutes.
Cool in the pan for 5 to 10 minutes. Lift out of pan and spread glaze over warm brownies.