Cut the roast in small strips (fajita style), and brown it in a hot pan.
While the meat is browning shred the cheese, slice the tomatoes, chop the green pepper, and dice the onion.
After meat is browned, drain off any fat and add taco seasoning along with a half cup of water. Bring up to a simmer.
Once everything is prepared, lightly grease a 13x9 baking dish and layer ingredients starting with tortillas, then a layer of meat, followed by the tomatoes, green peppers, and onions. Repeat layering, reserving the cheese for the top.
Cover pan with aluminum foil and bake for 45 minutes Remove foil and continue to bake uncovered for additional 15 mins, until cheese just begins to brown.
You could also add a can of bean (black beans or pinto) as an additional layer if you wish. I would have included in the recipe but I don't happen to have any on hand.