Spray a non-stick frypan with oil and heat over medium heat. Add beef, onion, and garlic and cook for 5 minutes, or until beef is brown. Add capsicum, taco seasoning, (chilli optional) and 1 tablespoon of water and cook for a further 3 minutes, or until sauce thickens.
Line an ovenproof dish with baking paper and place tortilla in baking dish.
Spoon beef mixture and chopped tomatoes down the middle of the tortilla and wrap it up so the edges of the tortilla join up. Pour tinned tomatoes over tortilla and sprinkle with cheese.
Cook in oven for 15 minutes, or until cheese is melted and golden.