Brown the onion in a little butter. Add ground beef and brown. Drain grease. I tip the pan and soak up the grease in paper towels. Season to taste. It is hard to tell you how much to put in.I just add and taste. You may want to add just a little more when you think you have it because you are going to mix in the the other ingredients and the spices will be diluted. Stir in tomatoes and and chilies. Mix well. Add about 3/4 of the mac. Mix well. Discard rest unless you want to add it in. Blend in 2 cups of the cheese. Top with remaining 2 cup of cheeze. Bake about 30 min ~~at; 350