This is one of my Mama's recipes that she taught me to many years ago to remember. It is so simple but very good. I have to bake this alot for my family. I really don't have a measurement for the peanut butter because Mama told me just to put on big glob, but her glob looked like about 1/2 cup. I have never measured it either I just put in what I think looks good.
Cook cake mix according to package direction in a 9"x13" pan. Let cake cool about 5 minutes and with the handle of a wooden spoon poke holes all over cake. In 2 quart boiler add sugar, milk, and margarine. Bring to a rolling boil over medium heat. Remove from heat as soon as it starts boiling, add peanut butter and stir until mixed. Pour over cake.