01 - Whisk together mayonnaise, ketchup, yellow mustard, sweet pickle relish, white vinegar, smoked paprika, and black pepper in small bowl until smooth and fully incorporated. Set aside at room temperature.
02 - Place large skillet or griddle over medium-high heat for 3-5 minutes until surface is thoroughly hot and smoking slightly.
03 - Divide ground beef into 8 equal portions, rolling each into compact ball. Season generously on all sides with kosher salt and freshly ground black pepper.
04 - Place beef balls on hot skillet. Immediately press down firmly with heavy spatula to smash into thin, wide patties. Cook undisturbed for 2-3 minutes until deep brown crust forms. Flip and cook 1-2 minutes longer until cooked through. Transfer to plate.
05 - Distribute mixed salad greens evenly among four large bowls. Arrange cherry tomatoes, red onion slices, dill pickles, and avocado sections atop greens in decorative pattern.
06 - Place 2 cooked smash patties in each bowl. Sprinkle shredded cheddar cheese over patties while still warm. Garnish with crispy fried onions if desired.
07 - Drizzle prepared smash sauce generously over each bowl. Serve immediately while patties remain warm and vegetables retain crisp texture.