Add 2 tablespoons of oil to a large frying pan over medium heat and heat for 1 minute.
Place in the onions, gently season with salt and saute for 5 to 7 minutes or until lightly browned. Turn the heat down to low and cook while occasionally stirring for 20 to 25 minutes or until well browned and tender. Set to the side.
In the meantime, ground beef should be formed into 4 equal-sized patties. Season them with salt and pepper.
You can either bake the bacon in the oven or cook it until crispy in the pan you plan on cooking the beef in. The latter option allows you to cook the burgers in the rendered bacon fat for more bacon flavor.
Add a few tablespoons of oil to a griddle or large cast iron skillet over medium-high heat. Heat for 1 minute.
Place the burgers onto the griddle or skillet and cook for 2 minutes untouched. Flip over, place on the cheese, and cook for an additional 1 minute to 90 seconds or until browned and cooked throughout. It’s ok to cook these in batches if there is no room. This is also when I toast the buns. I add them to the sides of the burgers and cook in the rendered fat until toasty.
Remove the burgers and set them to the side on a plate.
Assemble the burgers by adding lettuce to the bottom toasted buns and layering on tomatoes, pickles, a cheeseburger patty, bacon, caramelized onions, sauce, and the top toasted bun.
Notes
The crispier the bacon, the better your bacon burgers will be. To ensure extra crispness, start by cooking the bacon in a cold pan (or oven) to render the fat gradually. This will yield evenly crisp, golden-brown strips. Let the bacon sizzle over medium-low heat, flipping occasionally, and drain it on a paper towel-lined plate to prevent it from getting soggy.Handle the meat as little as possible: Overworking and compacting the ground beef leads to dense or tough burgers. Instead, gently shape the patties until they hold together to keep them tender, juicy, and flavorful.Make an indentation in the center: I press a slight dent into the middle of each patty with my thumb before cooking. This prevents the burgers from puffing up in the center as they cook.Let the burgers rest: Just like steak, burgers should be let rest for at least 5 minutes after cooking. This gives the natural meaty juices time to soak back into the meat, yielding more flavor and moisture in burgers.Grill the burgers instead: To add a smoky char, heat your outdoor grill to medium-high heat and grill the patties for 3 to 4 minutes per side for medium doneness. Add the cheese at the last minute and close the lid to help it melt and infuse the burgers with extra smoky flavor. Make-Ahead: Shape the burger patties and store them in an airtight container in the refrigerator for up to 24 hours before cooking. Wait to season the patties until just before cooking, as the salt can dry the meat. How to Store: Leftover cooked burgers can be stored in an airtight container in the fridge for up to 3 days, and leftover bacon can be kept covered in the fridge for up to 5 days. How to Reheat: Heat the burgers in a skillet over medium heat for 2 to 3 minutes per side or until warmed. To keep the bacon crispy, reheat it in a skillet for 1 to 2 minutes.