Make the sauce by combining all the ingredients in a small bowl. Set this aside until needed.
Make 2 patties by rolling 2-ounce portions of beef into balls and forming them into 4-inch circles on wax paper. Season one side of burger with Uncle Dibbz Texas Steak Rub
Preheat large sauté pan over medium/low to medium heat. Start at medium/low and then turn up the heat if needed after 5 minutes of pre-heating.
Add oil to pan and cook diced onions til browned. Remove and set aside.
Cook the beef by placing two patties seasoned side down in the hot pan. spread mustard over each patty. Cook for 2 minutes then flip each patty over. The beef should be nicely seared.
Immediately after flipping the beef add a slice of American cheese on top of each patty. Spoon cooked onion on top of each burger. Cook the patties for another 2 minutes.
While the patties cook, prepare the bottom of the hamburger by adding about 1 1/2 tablespoons of spread onto the face of the bottom bun. Stack the tomato slice on next. Pick up a small handful of lettuce and add it on top of the tomato.
When the patties are done, use a spatula to stack the burgers on top of each other and place on bottom bun. Top with other bun and serve.