Heat ghee in a pan over medium heat.
Sauté onion. garlic and fresh ginger until translucent.
Add in diced serrano pepper and cook for a minute.
Stir in diced tomatoes and add coriander powder, cardamom, paprika, turmeric, garam masala and salt to the onion and tomato combination.
Stir and cover the pan to let the vegetables and spices cook together for a few minutes.
Pour in water and coconut milk. Bring it to a slow simmer.
Add in chunks of Alaska cod and nestle them in the sauce.
Let the curry simmer and the cod cook for about ten minutes until the fish is cooked completely.
Serve warm with basmati rice, lime and fresh tomatoes.