Step 1

Heat 2 teaspoons oil in a 10-inch skillet over medium heat; cook and stir onion and green bell pepper in the hot oil until onions are softened, 5 to 10 minutes. Season mixture with salt and transfer to a bowl.

Step 2

Brush 1 side of each tortilla with remaining oil. Place 1 tortilla, oil-side down, in the same skillet; sprinkle with 1/2 the steak, 1/2 the onion mixture, and 1/2 the Mexican cheese mixture. Place a second tortilla, oil-side up, onto cheese layer, pressing down with a spatula to seal.

Step 3

Cook quesadilla over medium heat until cheese melts and tortillas are browned, 3 to 4 minutes per side. Remove quesadilla from skillet and cut into wedges. Repeat with remaining ingredients for second quesadilla.