Bring 250ml / 8fl oz (1 cup) water to a boil in a large, heavy-based pan, add the tomatoes, 1/2 teaspoon each of the ginger and garlic pastes, the curry leaves, fenugreek seeds, and cumin seeds and, cook for 10 minutes.
Pass through a sieve (strainer) to make a smooth puree.
Heat the oil in a large, heavy-based pan over medium heat, add the onions and fry for about 5-7 minutes, or until golden brown.
Add the remaining ginger and garlic pastes and fry for about 2 minutes. Add the pureed tomatoes, turmeric, chilli powder, and sesame seeds, then season with salt.
Put the roasted gram flour in a small bowl, add a little water and stir together, then add to the pan.
Add a little more water, if required. The dish should have a thick soup-like consistency. Simmer over medium heat for about 10 minutes.