Goan Fish Curry

A very well written recipe, borrowed from here:

https://www.recipetineats.com/goan-fish-curry-indian/

4 servings.

Curry paste:

2 1/2 tbsp Kashmiri chilli powder
1 tbsp coriander
2 tsp cumin
1 tsp turmeric
1/2 tsp fenugreek powder
3/8 tsp ground cloves
6 cloves garlic , minced
1 tbsp fresh ginger, finely grated
2 tbsp tamarind puree
1/2 red onion, chopped
90 ml water (plus more, as needed)

Curry:

3 tbsp vegetable oil
1/2 tsp black mustard seeds
1/2 red onion , cut in half again and thinly sliced
1 tbsp tomato paste
165 ml tomato passata or crushed tomato
165 ml water
400ml/ 14oz coconut milk , full fat
1 1/4 tsp salt
1 1/2 tsp sugar
1/4 tsp chilli powder
2 long green chillies , cut into half lengthwise and deseeded
1 tomato , cut into 8 wedges then into 2.5cm / 1" chunks
600g / 1.2 lb firm-fleshed white fish , cut into 3cm / 1.25" cubes

Garnishes / serving:

1/4 cup fresh coriander/cilantro leaves
Finely sliced green chillies , optional
Basmati rice

Curry Paste:

Place Curry Paste ingredients in a tall jug or milkshake container then blitz on high for 5 to 10 seconds until the onion is pureed. Add more water if needed to make it puree.

Curry:

Sizzle black mustard seeds: Heat oil over medium heat in a large pot. Add black mustard seeds and let them sizzle for 30 seconds

Saute onion: Add red onion and cook for 3 minutes until edges start to tinge with gold.

Add curry paste and cook for 3 minutes - to evaporate water, make spices bloom and cook garlic & ginger.

Turn heat up to medium high. Add tomato paste and tomato pulp, cook for 2 minutes.

Add water, coconut milk, sugar, salt and chilli powder if using. Stir, then bring to simmer, low heat so it's bubbling gently.

Simmer 2 minutes, add tomato & green chilli: Simmer for 2 minutes, add tomato and green chilli.

Simmer for another 3 minutes, stirring every now and then - sauce should be thickened (not watery), it gets looser again when fish is added.

Add fish, stir, cook for 3 to 4 minutes until fish easily flakes.

Remove from stove and transfer to serving bowl. Garnish with coriander/cilantro and fresh green chillies if desired.