01 - Whisk together mayonnaise, ketchup, yellow mustard, sweet pickle relish, white vinegar, smoked paprika, and black pepper in a small bowl until smooth. Set aside.
02 - Place a large skillet or griddle over medium-high heat until hot.
03 - Divide ground beef into 8 equal balls. Season evenly with kosher salt and black pepper.
04 - Place beef balls onto the hot skillet. Press each ball down firmly with a heavy spatula to create thin patties. Cook undisturbed for 2-3 minutes until the edges are crisp and deeply browned. Flip and cook for an additional 1-2 minutes. Remove from heat.
05 - Distribute salad greens evenly among four bowls. Arrange cherry tomatoes, red onion, dill pickles, avocado slices, and shredded cheddar cheese on top of the greens.
06 - Place the cooked smash burger patties over each prepared bowl, distributing evenly.
07 - Drizzle the smash sauce generously over each bowl. Sprinkle with crispy fried onions if desired. Serve immediately while the patties are still warm.