Make the dressing. In a small bowl, whisk Greek yogurt (or mayo), ketchup, mustard, relish, vinegar, paprika, salt, pepper, and hot sauce if using. Taste and adjust. It should be tangy, slightly sweet, and creamy.
Chill while you prep everything else.
Prep the veggies. Chop romaine/iceberg, tomatoes, pickles, cucumber, and red onion. Dice avocado last so it stays fresh. Keep ingredients in separate bowls if you’re meal-prepping.
Cook the beef. Heat a large skillet over medium-high.
Add a drizzle of oil if using lean beef. Sauté half the diced onion until softened, about 2–3 minutes. Add garlic for 30 seconds.
Crumble in the beef and season with salt, pepper, smoked paprika, and onion powder. Cook, breaking it up, until browned with some crispy bits, about 6–8 minutes. Drain excess fat if needed.
Melt the cheese. Reduce heat to low.
Sprinkle shredded cheddar over the beef and let it soften, or fold in chopped American slices. Stir gently until melty and evenly distributed.
Assemble the base. Add chopped lettuce to a large serving bowl. Scatter tomatoes, pickles, cucumber, and the remaining raw onion over the greens.
Add the beef and toppings. Spoon the cheesy beef over the salad.
Add crumbled bacon, avocado, and sesame seeds if using.
Dress and toss. Drizzle with the special sauce dressing. Toss lightly so every bite gets some sauce without crushing the greens. Serve right away while the beef is warm for the best burger effect.