Heat coconut oil in a pan over medium-high heat.
Once the oil is hot, add mustard seeds, fennel seeds, and fenugreek seeds, and let them crackle for 4-5 seconds.
Add onions and cook until the onion turns slightly brown in color (8-10 minutes), stirring frequently.
Add tomatoes, green chilies, ginger, garlic, and curry leaves, and cook for 3-4 minutes until the tomatoes are mushy.
Now add coriander powder, turmeric powder, chili powder, pepper powder, and garam masala powder, and cook for a minute.
Add 1 cup of water, tamarind paste, and salt, and mix well. Reduce the heat to low.
Cover the pan with a lid and cook for 3-4 minutes, stirring a few times while cooking.
Now add coconut milk (optional) and ½ cup of water and bring the curry to a simmer, stirring frequently.
Add prawns and cook for 5-6 minutes.
Check for salt and add more if required. Garnish the curry with chopped cilantro.
Heat coconut oil in a small pan.
Once the oil is hot, add shallots (or onions) and curry leaves, and fry until the shallots are browned, stirring frequently.
Add Kashmiri red chili powder and saute for 3-4 seconds.
Pour the tempering over the curry and mix well. Serve hot.