Cheddar Burgers With Balsamic Onions and Chipotle Ketchup

Ingredients

Onions

• 1 lb red onion, cut crosswise into 1/3 to 1/2 inch rounds
• olive oil
• 3/4 teaspoon kosher salt
• 1/2 teaspoon fresh coarse ground black pepper
• 2 tablespoons balsamic vinegar

Chipotle Ketchup

• 1 cup ketchup
• 1 1/2 teaspoons chopped chipotle chilies, from canned chipotle chilies in adobo
• 2 tablespoons adobo sauce, from can
• 2 teaspoons balsamic vinegar

Burgers

• 2 1/4 lbs 80% lean ground beef (15%-20% fat)
• coarse kosher salt
• 6 slices sharp cheddar cheese (thick slices)
• 6 large English muffins or hamburger buns, split & grilled
• 6 slices tomatoes
• 2 cups fresh spinach leaves

Directions

1. 1

   Onions:.

2. 2

   DO AHEAD; CAN BE MADE UP TO 3 DAYS AHEAD! Prepare grill to medium high heat. Arrange onion rounds on baking sheet. Brush with oil; sprinkle with 3/4 teaspoon coarse salt and pepper. Transfer onion rounds to grill rack; close cover. Cook until onions are tender, about 10 minutes. Transfer to a medium bowl. Toss with vinegar. Cover and chill.

3. 3

   Chipotle Ketchup:.

4. 4

   DO AHEAD; CAN BE MADE UP TO 3 DAYS AHEAD!

5. 5

   Mix ketchup, chilies, adobo sauce, and 2 teaspoons vinegar in small bowl. Season with salt and more vinegar, if desired. Cover and chill.

6. 6

   Burgers:.

7. 7

   Shape beef into 6 1/2 inch-thick patties. Sprinkle patties on both sides with coarse salt and pepper.

8. 8

   Prepare grill to medium high heat. Place burgers on grill. Close cover; cook burgers until bottoms start to darken and juices rise to surface, about 3 minutes. Turn burgers; cook to desired doneness, about 3 minutes longer for medium-rare. Top with onions and cheese. Close cover; cook until cheese melts.

9. 9

   Place grilled English muffin or bun bottoms on plates; spread with ketchup. Top with burgers, tomatoes, spinach, and grilled muffin tops. Serve, passing remaining ketchup separately.