Begin by preparing the sauce: in a small bowl, whisk together the mayonnaise, ketchup, mustard, relish, and hot sauce. Set this mixture aside to allow the flavors to meld.

Heat a griddle over medium-high heat, ensuring the surface is adequately hot for cooking.

Divide the ground beef into four roughly equal portions, shaping them into mounds and placing them on the griddle. Evenly season each with Kosher salt and freshly ground black pepper. Allow the beef to cook for about two minutes.

Lay a flour tortilla on top of each beef mound, gently pressing down to flatten the beef to match the size and shape of the tortilla. Cook until the tortilla turns golden-brown, approximately 2 to 3 minutes.

Flip each patty, placing a slice of American cheese on top. Continue cooking until the cheese is fully melted and the tortilla has lightly browned.

Remove from the griddle and layer the tacos with shredded lettuce and diced onions. Drizzle with the prepared sauce, then fold each taco in half. Serve immediately for the best experience.