In a skillet over medium heat, brown the ground beef with the onion, crumbling it as it cooks. Drain any excess fat.

Add the taco seasoning, jalapeno pepper, and diced tomatoes with their juices. Bring to a boil, then reduce and simmer for 10 minutes.

Sprinkle cheese on one half of a tortilla, then spread on some of the meat mixture. Fold the tortilla over and press to seal. Continue until all tortillas are filled.

Wipe out the skillet and return it to the stovetop over medium heat. Add a tablespoon of oil. Place the folded tortillas in the pan and fry for a couple of minutes on each side until browned and crispy.

Serve with avocado, sour cream, and salsa.