Step 1

Heat oil in pan and add onions.

Step 2

Cook onions covered, over medium heat for 30 minutes or until onions begin to turn golden brown and caramelize. Watch them so they don't burn.

Step 3

Remove lid and cook for 5 more minutes and then add 1/2 C water. Allow water to evaporate.

Step 4

Set aside, onions can be made several days ahead of time and refrigerated.

Step 5

Mix together the mayo, ketchup, relish and vinegar in a bowl and set aside.

Step 6

Form meat into 8 patties about 4 inches wide and 1/2 inch thick.

Step 7

Heat griddle and lightly brush with vegetable oil.

Step 8

Toast the buns on the griddle, split side down.

Step 9

After they are toasted golden brown spread the bottom bun with 1 Tbsp of the mayo mixture.

Step 10

Top with tomato and lettuce.

Step 11

Salt and pepper both sides of hamburger patties and cook on the griddle for 3-5 minutes.

Step 12

Spread top of patty with 1 1/2 tsps mustard and flip.

Step 13

Top patty with cheese and allow to cook until desired doneness.

Step 14

Add hamburger to bun and top with caramelized onion.