Spray four 6x6-inch pieces of aluminum foil with cooking spray. Place salmon fillets on top.
Drizzle lemon juice over salmon fillets; sprinkle 1/2 teaspoon of dill weed over each one. Spread 1 tablespoon mustard onto each salmon fillet; top with dill pickle and onion. Wrap aluminum foil around salmon, sealing the edges. Place packets onto a baking sheet.
Bake in preheated oven until fish flakes easily with a fork, about 15 minutes.
Place packets in shallow bowls; open with heatproof gloves. Top with diced tomatoes and sport peppers; season with celery seed.
