Sprinkle the fish with the olive oil, salt and pepper, and place into a deep dish. In a small bowl, combine the mustard and thyme. Mix together and spread onto both sides of the fish. Top with the lemon zest and juice. Put in the fridge to marinate for 2 to 3 hours.
Preheat a deep fryer to 350 degrees F.
In a small bowl, combine the cornmeal and flour together. Sprinkle the crab boil seasoning on top of the fish and dredge in the cornmeal mixture. Place in the deep fryer for 3 to 4 minutes, and then remove to paper towels. Serve with Tomato Relish.
In a small bowl, combine the tomatoes, cilantro, garlic, onions, jalapeno and lime zest and juice. Cover and chill for up to 3 days.