Mix the pepper into the ground meat and form into patties about ¼ inch thick making sure the patties are slightly bigger than the buns you plan to use. Place a teaspoon of yellow mustard on one side of each patty.

Using a grill, griddle or pan, cook the patties on medium head, mustard side up, until the bottom of the patty is brown and cooked. Flip the patty over so the mustard side gets cooked through and cook until desired liking. Place a slice of American cheese on the patty and let melt slightly. Remove the patties from the heat and set aside.

In a pan over medium heat, add 2 tablespoons olive oil and the diced onions with a bit of salt. Cook until brown and slightly caramelized, about 7 minutes. Remove from pan. Add another tablespoon of olive oil and place the buns open side down onto the heat until slightly crisp and golden brown. Repeat for the rest of the buns.

Add all the ingredient for the sauce into a bowl and mix. Assemble burgers as desired, and enjoy!