In a separate bowl, use a spatula to toss the onion, celery, relish, Worcestershire sauce, sugar, mustard, garlic powder, salt, and pepper together until evenly combined.
1/4 cup finely minced white onion, 1/4 cup minced celery, 3 tbsp dill relish, 1 tsp Worcestershire sauce, 1 tbsp sugar, 1 tbsp yellow mustard, 1/2 tsp garlic powder, salt and pepper