Heat small amount of olive oil in a small skillet over medium-low heat.
Add onion slices and cook until golden brown and caramelized, turning occasionally. Remove from heat and set aside.
Fry bacon in a separate skillet until crispy. Drain on paper towel and set aside.
Divide ground beef into 4 equal sized burgers and fry in a skillet until cooked thru. Just before the burgers are done, place a slice of cheese on each burger and cover pan with a lid to melt the cheese.
Toast buns in a pan over medium - high heat.
Place a Tablespoon of garlic aioli on the bottom bun.
Top with a cheese burger patty, 2 slices of bacon and some of the caramelized onions, lettuce and tomato.
Place second half of bun on top and serve.
I only had spring mix lettuce, so that is what I used.
There are only 3 cheeseburgers shown in the pan, because my son's has to be removed before the cheese goes on!