Season the fish fillets with salt and pepper. Set aside.
Heat the vegetable oil in a large skillet over medium heat.
Add the chopped onion, minced garlic, and grated ginger to the skillet. Cook for about 2-3 minutes until the onion is translucent.
Stir in the turmeric powder, ground cumin, and ground coriander. Cook for an additional minute until the spices are fragrant.
If using, add the finely chopped green chili. Add the cherry tomatoes and cook for about 2 minutes until they start to soften.
Pour in the coconut milk, fish sauce, and soy sauce. Stir to combine and bring to a gentle simmer.
Gently place the fish fillets into the skillet. Spoon some of the sauce over the fish. Cover and cook for about 8-10 minutes, or until the fish is cooked through and flakes easily with a fork.
Stir in the fresh lime juice and adjust seasoning with salt and pepper to taste.
Garnish with fresh cilantro and serve hot with steamed rice or bread.
Enjoy your meal!