Heat oil in a large pan over medium heat.
Add chopped onions and sauté until golden brown.
Stir in ginger-garlic paste and green chilies, and cook for 2 minutes.
Add chopped tomatoes and cook until soft.
Mix in curry powder and cook for another minute.
Pour in coconut milk and bring to a simmer.
Add fish fillets, making sure they are submerged in the sauce.
Cook for 10-15 minutes until fish is cooked through.
Season with salt to taste.
Garnish with fresh cilantro before serving.