Preheat the oven to 350 degrees Fahrenheit (177 degrees Celsius).
If your burgers are not thin patties, flatten out them with a rolling pin after sandwiching them between two sheets of parchment paper.
Place the burger patties on a foil-lined baking tray and cook as per cooking instructions on the packaging.
Slice the white onion into thin discs
Once the burger patties are done, place the patties onto the bottom burger bun.
Top each burger patty with 1 tablespoon ketchup, 1 tablespoon mayonnaise, 2 discs of white onion, 3 slices of pickle slices, 2 slices of beefsteak tomato, and 1 large leaf of curly lettuce.
Repeat this process with the second burger
Cover the burgers with the top part of the bun and enjoy.