Begin by heating olive oil in a skillet over medium heat. Add the sliced onions and bell peppers and sauté them until they soften and become tender. Add the cooked steak to the pan, season with salt and pepper, and stir to combine. Take one tortilla and fill it with half of the steak mixture and half of the shredded cheese. Place the second tortilla on top, then cook the quesadilla in the skillet until the bottom is golden brown. Flip it over to crisp the other side. Once it’s fully cooked, remove it from the skillet, slice into wedges, and enjoy hot.