Spray a large, non-stick skillet with non-fat cooking spray and set over medium-high heat. Add in garlic okra, bell pepper, onions, and celery. Cook until veggies are tender, about 5-7 minutes. Transfer to a bowl and set aside.
Make the roux by adding the butter to the skillet, and then add in the flour; stir until blended. Continue to cook, stirring constantly until the flour is well browned, but not burned, about 8-10 minutes.
Slowly drizzle in the broth into the skillet, continuously stirring to remove lumps, and bring to a slow simmer. Add in the thyme, bay leaves, salt, pepper, lemon juice, and tomatoes.
Add the cooked vegetables back into the skillet and simmer for about 5 minutes.
Stir in the shrimp and crabmeat and simmer until shrimp are cooked, about 3-5 minutes.