Spanish Rice

This is one of Grandma Anderson's recipes, a family favorite.  Chase just requested that I (Bev) bring a dish of this with me when I come tomorrow to see him and Danielle (just recently admitted to the hospital).  After looking through the cupboard, I was able to find this original recipe!

3 small onions
2 lbs. hamburger
2 T. butter
2 tsp. salt
1 green pepper, chopped
1/4 tsp. black pepper
3 cups stewed tomatoes
2 cups cooked rice
2 T. prepared mustard

Cook onions, peppers in butter till brown.  Add meat, salt, pepper, mustard and stir constantly till meat is seared well.  Butter baking dish and add alternating layers of meat and rice until all is used.  Pour tomatoes over all.  Bake 1 hour at 350.  Serve hot.