Sweet and Sour Meatloaf

Okay I know.... not everyone likes meatloaf - but we love this recipe! (My grandpa's)

Sweet and Sour Meatloaf
1 T. of Mustard
8 0z of catsup
1/4 cup vinegar
1/4 cup brown sugar
(Mix together and heat. Take half of it and pour in a bowl.) (I often double the sauce)
add 1 small chopped Onion
1 cup crushed crackers or (Grandpa used 2 cups oatmeal.)
1 egg
Hamburger about 1 lb or 1 1/2 lbs
Salt and Pepper (I often add garlic etc...)
Pour rest of catsup mixture on top and mix really well save soon to put just on top.
I often add finely chopped carrots - mushrooms - celery etc.
Bake 350 degrees for 1 hr.
When done put shredded cheese on top and melt. enjoy