Heat olive oil in a large skillet over medium heat. Add diced onions and cook for 3-4 minutes until onions begin to soften.
Reduce heat to medium low and add ground beef, garlic powder and paprika to the pan, breaking up the meat. Stir occasionally and cook until the ground beef is completely browned/cooked through. Add Worcestershire sauce, ketchup and mustard. Allow to cook for an additional 4-5 minutes on low, stirring regularly.
While the beef is cooking, make the big mac sauce by combining all ingredients in a small bowl. Set aside.
Assemble the sloppy joes on buns with meat, plenty of big mac sauce, lettuce, onion, cheese and plenty of big mac sauce.
Notes
Estimated nutrition information doesn't include buns or toppings.