Brown meat with minced onion until meat is cooked through. Drain off any liquid/fat.
Add in taco seasoning. chilies and tomato sauce and simmer until liquid is absorbed.
Place taco shells into baking dish with rolled up foil on the bottom to keep shells from touching the bottom of the pan.
Fill shells with meat mixture and top with cheese.
Bake at 400 degrees for 10-12 minutes or until cheese melts and the shells are heated through.
Remove from oven and top with desired condiments.
Place two pieces of rolled up foil in the bottom of the pan to allow for drainage and keep the tacos from sitting in any grease or liquid that may run off from the tacos. If your meat isn't well drained, you may get some liquid draining out of the shells and if the taco shells are sitting flat on the pan they can get soggy.