Brush fish fillets with oil and season with salt, pepper, and Creole seasoning. Set aside.
In a skillet over medium heat, melt butter or oil. Sauté garlic until fragrant, then add diced tomato, red bell pepper, broth, lemon juice, Creole seasoning, salt, pepper, and bay leaf. Simmer for about 10 minutes.
In a pot, bring water to a boil. Gradually stir in grits and salt; reduce heat to low and cook, stirring frequently, until thickened, about 20 to 30 minutes.
Once grits are nearly done, stir in shredded cheddar cheese until melted and creamy.
In another skillet over medium-high heat, cook the fish fillets for 4 to 5 minutes per side until golden brown and cooked through.
Serve the cheesy grits topped with the cooked fish and spoon the tomato-based sauce over the top.