Step 1: Prepare the Burger Sauce. In a small bowl, whisk together the sugar-free mayonnaise, yellow mustard, and smoked paprika. Set this aside in the refrigerator to allow the flavors to meld while you prepare the rest of the meal.
Step 2: Season the Chicken. In a medium mixing bowl, gently combine the ground chicken with the salt, black pepper, garlic powder, and onion powder. Divide the mixture into four equal-sized balls. Do not flatten them into patties yet.
Step 3: Heat the Skillet. Place a large cast-iron skillet or non-stick pan over medium-high heat and add the oil. Wait until the oil is shimmering and the pan is very hot to ensure you get a good sear on the meat.
Step 4: Smash the Chicken. Place the chicken balls onto the hot skillet. Use a sturdy spatula (and a second tool to press down if needed) to smash each ball into a very thin patty. Cook for about 3-4 minutes until the edges are dark brown and crispy.
Step 5: Flip and Finish. Flip the patties carefully and cook for another 2-3 minutes on the other side until fully cooked through. Remove the patties from the heat and let them rest for a minute.
Step 6: Assemble the Bowls. Divide the chopped romaine lettuce between two bowls. Top with the halved tomatoes, sliced pickles, red onion, and avocado. Place two chicken patties into each bowl and drizzle generously with the prepared burger sauce.