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 the ground beef into 8 equal portions and roll into balls. Season generously with kosher salt and freshly ground black pepper on all sides.
04 - Place beef balls on the hot skillet. Press each ball firmly with a heavy spatula to smash into thin, wide patties. Cook undisturbed for 2-3 minutes until a deep brown crust forms. Flip and cook 1-2 minutes longer for medium doneness. Remove to a plate.
05 - Distribute mixed greens evenly among four serving bowls. Arrange cherry tomatoes, red onion slices, dill pickles, and avocado on top of each bed of greens.
06 - Place two crispy smash patties on each salad bowl, allowing them to rest slightly on the greens.
07 - Drizzle each bowl with prepared smash sauce, sprinkle with shredded cheddar cheese and crispy fried onions. Serve immediately while patties are still warm.