Heat oven to 350 degrees.
In 9" pan, ungreased, sift flour, sugar, baking powder and salt.
Add milk, oil and vanilla. Mix with a fork. Stir in peanut butter.
Spread evenly. Sprinkle with 3/4 c. brown sugar.
Pour hot water over batter. Bake for 40 minutes.
Serve warm with ice cream or whipped topping.