Clean and crack the crabs so the curry can absorb into the meat.
Heat oil in a pot and add cumin seeds and cinnamon stick. Let them sizzle.
Add onions and fry until golden brown.
Add garlic, ginger, and green chillies. Cook for 1–2 minutes.
Add curry powder, turmeric, chilli powder, and salt. Stir well to form a thick spice base.
Add tomatoes and cook until soft and the oil starts to separate.
Add the crab pieces and coat them well in the masala.
Pour in a little water to create a gravy and bring to a simmer.
Cover and cook for 15–25 minutes until crab is fully cooked and flavours are absorbed.
Adjust seasoning, add fresh coriander, and finish with lemon juice.
Serve hot with rice or roti.