In a medium saucepan, bring the water or broth to a boil. Stir in the grits, reduce the heat to low, cover, and simmer, stirring occasionally, for 20–25 minutes or until thick and tender.
Once the grits are cooked, stir in the butter, cheddar cheese, and heavy cream (if using). Season with salt and pepper. Keep warm.
In a small bowl, combine the paprika, garlic powder, onion powder, thyme, oregano, cayenne, black pepper, and salt. Rub the seasoning all over the fish fillets.
Heat olive oil or butter in a large skillet over medium-high heat. Add the fish and cook for 3–4 minutes per side, or until the exterior is nicely blackened and the fish flakes easily with a fork.
Spoon a generous serving of cheese grits onto each plate. Top with a piece of blackened fish. Optionally garnish with chopped parsley, a squeeze of lemon, or hot sauce.