The Mesa Grill Burger with Double Cheddar Cheese, Grilled Vidalia Onion, and Horseradish Mustard

1/4 c Dijon Mustard
1 T prepared Horseradish, drained
1 large Vidalia onion, sliced crosswise into 1/2 slices
2 T Canola Oil
Kosher Salt and Freshly Ground Black Pepper
2 lbs ground Chuck
8 slices Cheddar Cheese (preferably a mix of white & yellow)
4 slices beefsteak tomato
4 lettuce leaves

1. Whisk together the mustard and horseradish in a small bowl; set aside.
2. Preheat a grill to high or a grill pan over high heat.
3. Brush the onion slices with the oil on both sides and season with salt and pepper.
4. Grill the onion slices for 3-4 minutes on each side, until lightly golden brown.
5. While the onion is grilling, form the meat into 4 burgers.
6. Season the burgers on both sides with salt and pepper.
7. Grill for 3 to 4 minutes on each side for medium.
8. Add 2 slices of the cheese to the top of each burger, cover the grill and let melt about 1 minute.
9. Place the burgers on the buns sandwiched with onion, tomato, lettuce and a dollop of horseradish mustard.

[ as seen in "BOBBY FLAY'S MESA GRILL COOKBOOK, explosive flavors from the southwestern kitchen" by Bobby Flay, Stephanie Banyas and Sally Jackson ]