Heat the ghee in a large saucepan, add the onion, garlic and ginger, sweat until the onions are soft.
Add the cumin, coriander, chilli, cinnamon, salt and turmeric. Then stir in the peas until everything is well mixed.
Add the tomatoes together with the juice, mash lightly. Add water and bring everything to a boil. Reduce to low heat and simmer without lid for about 40 minutes, until most of the liquid has been absorbed and the peas are soft. Gradually stir in Garam Masala and season to taste.