Preheat oven to 425 degrees. Place the fish on a sheet pan, and pat dry.
Combine the lemon zest, mustard, old bay, garlic powder, and 1 TBSP oil. Brush on top of the fish.
Combine the melted butter, crushed crackers, and fried onions. Divide on top of the fish, and press lightly to adhere.
Place the broccoli on the other side of the pan. Drizzle with remaining oil, salt, pepper, and garlic powder.
Roast 10-15 minutes, or until fish is golden brown and cooked through.
Combine the lemon dill sauce ingredients in a small bowl, and serve on the side for dipping, along with lemon wedges.