01 - Whisk together mayonnaise, ketchup, yellow mustard, sweet pickle relish, white vinegar, smoked paprika, and black pepper in a small bowl until smooth and fully incorporated. Set aside at room temperature.
02 - Place large skillet or griddle over medium-high heat and allow to preheat thoroughly until surface is evenly hot.
03 - Divide ground beef into 8 equal portions and roll into balls. Season each ball generously with kosher salt and freshly ground black pepper.
04 - Place beef balls onto hot skillet. Press each ball down firmly with a heavy spatula to smash into thin, irregular patties. Cook undisturbed for 2–3 minutes until edges are crispy and bottoms are well-browned. Flip and cook an additional 1–2 minutes until cooked through. Remove from heat and set aside.
05 - Distribute mixed salad greens evenly among four serving bowls. Arrange cherry tomatoes, red onion slices, dill pickles, and avocado sections over the greens.
06 - Place 2 smashed burger patties on each bowl. Sprinkle shredded cheddar cheese evenly across all bowls while patties are still warm.
07 - Drizzle prepared smash sauce generously over each bowl. Top with crispy fried onions if desired. Serve immediately while patties remain warm.