In a blender, combine the chopped onion, garlic, ginger, green chilies, cumin, coriander, and turmeric. Blend to form a smooth paste.
Cook the Curry:
Heat 2 tbsp of vegetable oil in a large pan over medium heat. Add the finely chopped onion and cook until soft and translucent, about 5-7 minutes.
Add the minced garlic and grated ginger. Cook for another 2 minutes.
Stir in the spice paste and cook for about 5 minutes, stirring frequently to avoid sticking.
Add the chopped tomatoes and cook until they break down and form a thick sauce, about 10 minutes.
Stir in the curry powder, ground cumin, ground coriander, turmeric powder, and chili powder. Cook for 2 more minutes.
Simmer the Curry:
Pour in the coconut milk and water or seafood stock. Stir well to combine. Bring the mixture to a boil, then reduce the heat and let it simmer for 10 minutes.
Add the shrimp to the pan and cook until they are pink and opaque, about 5-7 minutes.