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 to allow flavors to meld.
02 - Place a large skillet or griddle over medium-high heat and allow it to get thoroughly hot.
03 - Divide ground beef into 8 equal portions and roll into balls. Season evenly with kosher salt and black pepper.
04 - Place beef balls on the hot skillet. Press each ball firmly with a heavy spatula to smash into thin patties. Cook undisturbed for 2–3 minutes until a deep brown crust forms. Flip and cook 1–2 minutes longer until desired doneness. Remove from heat.
05 - Distribute mixed salad greens evenly among four bowls. Arrange cherry tomatoes, red onion, dill pickles, avocado, and shredded cheddar cheese on top of the greens.
06 - Place the cooked smashed burger patties over each bowl. Drizzle generously with smash sauce and sprinkle with crispy fried onions if desired. Serve immediately while patties are still warm.