Spray an 8x8 baking pan with cooking spray and preheat the oven to 350º Fahrenheit.
Mix the flour, ¾ cup brown sugar, baking powder and salt in a bowl.
Add the milk, peanut butter, oil and vanilla. Mix well until smooth.
Pour the batter into the prepared pan.
Sprinkle the ½ cup brown sugar overtop the batter.
Pour the hot water over the top of the batter.
Bake for 30-35 minutes or until the cake part is set.
Allow the cake to cool for 20-30 minutes. The sauce underneath will thicken slightly as it sits. Serve with ice cream and use the sauce as a topping.
Notes
The calories shown are based on the cake being cut into 12 pieces, with 1 serving being 1 slice of cake. Since different brands of ingredients have different nutritional information, the calories shown are just an estimate. **We are not dietitians and recommend you seek a nutritionist for exact nutritional information.**