Add 2 teaspoons of fajita seasoning to ribeye, toss well to combine, and let rest
In large skillet, heat avocado oil over high heat. Add onions and bell peppers and saute, tossing occasionally, until charred. After about 3 minutes, turn heat down to medium add 1 teaspoon of fajita seasoning, and continue to saute for about 7 minutes, until bell peppers are tender-crisp. Remove onions and peppers and set aside
Add ribeye to skillet and cook for about 5 minutes, until brown. Return peppers and onions to skillet, toss to combine, and cook for another 3-4 minutes.
Spray another large skillet lightly with cooking spray. Lay one tortilla in skillet; top with half of steak and veggies mixture, and then half of the shredded cheese. Lay another tortilla on top. Take a flat pot cover and press down lightly on tortilla. Turn heat to medium and cook for 3 minutes per side, until tortillas are golden brown
Remove quesadillas from skillet and place on flat surface. Use a pizza cutter to cut quesadillas into pieces. Serve immediately