Make the sauce: In a small bowl, whisk together mayonnaise, sugar-free ketchup, mustard, relish, vinegar, paprika, salt, and pepper.
Taste and adjust. Chill while you prep the rest.
Prep the veggies: Chop the lettuce, slice the tomatoes and onions, and dice the pickles. Set out your cheese and optional avocado.
Cook the beef: Heat a large skillet over medium-high.
Add oil if your beef is very lean. Crumble in the ground beef and cook, breaking it up, until browned with crisp edges, 6–8 minutes.
Season it right: Stir in salt, pepper, garlic powder, onion powder, and smoked paprika. Add 1–2 teaspoons mustard and cook 30 seconds more.
Taste and adjust seasoning.
Build the bowls: Divide lettuce into 4 bowls. Top with warm beef, tomatoes, onions, pickles, and cheese. Add avocado if using.
Finish with sauce: Drizzle the burger sauce over the top.
Sprinkle sesame seeds for a fun touch. Serve immediately while the beef is hot and the lettuce is crisp.