Cheddar Burgers with Balsamic Onions and Chipotle Ketchup

Ingredients

• •1 pound red onions, cut crosswise into 1/3- to 1/2-inch-thick rounds
• •2 tablespoons Olive oil
• •¾ teaspoon coarse kosher salt
• •½ teaspoon coarsely ground black pepper
• •2 tablespoons balsamic vinegar
• •1 cup ketchup
• •1½ teaspoons chipotle chiles in adobo
• •2 teaspoons balsamic vinegar
• •2¼ pounds ground beef
• •1 teaspoon Coarse kosher salt
• •6 slices sharp cheddar cheese
• •6 pieces English muffins or hamburger buns
• •6 slices tomato slices
• •2 cups fresh spinach leaves

Cooking Instructions

1. 1.

   Prepare barbecue (medium-high heat): Arrange onion rounds on baking sheet. Brush with oil; sprinkle with 3/4 teaspoon coarse salt and pepper. Transfer onion rounds (still intact) to grill rack; close cover. Cook until grill marks appear, about 4 minutes per side. Reduce heat or move onions to cooler part of grill. Close cover; cook until onions are tender, about 10 minutes. Transfer to medium bowl. Toss with vinegar. DO AHEAD: Can be made 3 days ahead. Cover; chill.

   18 min

2. 2.

   Mix ketchup, chiles, adobo sauce, and 2 teaspoons vinegar in small bowl. Season with salt and more vinegar, if desired. do a h e a d Can be made 3 days ahead. Cover and chill.

   5 min

3. 3.

   Shape beef into six 1/2-inch thick patties. Sprinkle patties on both sides with coarse salt and pepper. Prepare barbecue (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. Place muffin bottoms on plates; spread with ketchup. Top with burgers, tomatoes, if desired, spinach, and muffin tops. Serve, passing remaining ketchup separately.

   15 min

4. 4.

   *Dried, smoked jalapeños in a spicy tomato sauce called adobo; available at some supermarkets and at specialty foods stores and Latin markets.