Simmer butter over medium heat until butter becomes a golden brown, whisking occasionally, for 3 to 5 minutes. Remove from heat, whisk in vinegar, honey, and Dijon mustard. Set aside 1/8 cup of sauce.
Rinse scallops under cool water then dry with paper towels. Sprinkle with salt and pepper. Heat a non-stick pan to medium-high heat. Spray pan with cooking spray and place scallops in pan and sear on each side for 2 minutes. Brush scallops using the separate portion of balsamic brown butter sauce and sear for 2 minutes, turn scallops and repeat. Continue until scallops are golden and completely cooked throughout, total cooking time should be approximately 10 minutes, when using larger scallops. Remove from heat and tent with foil.
Lay Spring mix on a plate and place scallops on spring mix and sprinkle capers and chopped tomatoes. Drizzle remaining sauce over entire salad.