Bacon Cheddar Burgers with Tomato Onion Jam

For the Tomato Onion Jam

• 1 tablespoon olive oil
• 1 sweet onion such as Vidalia, Maui, or Walla Walla, very thinly sliced, large
• 4 tomato small to medium
• 1 tablespoon white sugar
• 1 tablespoon brown sugar
• 2 tablespoons lemon juice from about ½ lemon, fresh
• 2 tablespoons apple cider vinegar
• 2 teaspoons kosher salt
• 1 teaspoon dry mustard powder
• pinch red chili flakes optional

For the Burgers

• 8 lices thick-sliced bacon
• 2 lbs ground chuck beef or 80/20 ground beef
• salt to taste
• black pepper to taste
• 4 sharp white cheddar cheese thick slices
• 4 large soft hamburger buns, with or without seeds
• tomato onion jam