Mix ketchup, egg, 1/2 tsp. salt, and pepper. Mix with ground beef, onions, and bread crumbs in a 9 inch pie pan.
Bake at 350°F for 30 minutes. Pour off fat.
Potato Topping: Mix green pepper, butter, pimientos, 1/2 tsp. salt, milk and potato mix. Pour in the instant potatoes till thick. Place the potato mixture on to the hamburger mixture. Place cheese on top of the potatoes and put back into the oven till the cheese melts.