Heat the olive oil in a large cast iron skillet over medium-high heat. When hot, add the beef and cook without moving for 4-5 minutes on each side, or until brown. Using a meat masher, break up the beef. Add the diced red onion and continue cooking for 3-4 minutes, or until the beef is no longer pink and fully cooked through. Mix in the taco seasoning, then mix in the water. Add 1.5 cups of the shredded cheese, and toss until melted.
Spread about 3 tablespoons of the cooked beef mixture on one half of a tortilla. Add a sprinkle of the remaining cheese. Fold over and press down, repeat with the remaining tortillas.
1o flour tortillas
Place the tacos in the air fryer basket in a single layer. Lightly spray the tops of the tortillas with olive oil spray and cook for about 4 minutes or until the outside of the tortillas are crisp. Repeat with the remaining tortillas.