1. Heat 1 tbl of the oil in a large skillet over medium heat. Add the chopped onion and cook, stirring occasionally, until beginning to soften, 2 to 3 mins. Add the beef, cayenne, 1/2 tsp salt and 1/4 tsp black pepper. Cook, breaking up the beef with a spoon, until no longer pink, 3 to 5 mins more.

2. Heat broiler. Brush one side of ea tortilla with 1 tsp of the remaining oil, Place 2 tortillas, oiled-side down, on a foil lined baking sheet. Top with beef mixture, Monterey Jack, and remaining tortillas (oiled-side up). Broil until crisp and the cheese melts, 1 to 2 mins per side.

3. Meanshile, in a large bowl, toss the watercress, corn, and sliced onion with the lime juice, the remaining tbl of oil, and 3/4 tsp each salt and black pepper. Cut the quesadillas into wedges and serve with the salad.