Fill your kettle and boil it. Peel and finely chop the onion. Dice the tomatoes. Warm a medium-sized pan over a medium heat for 2 mins, then add 1 tbsp oil and the chopped veg. Season with a pinch of salt and pepper. Fry, stirring often, for 5 mins till the veg are glossy and starting to soften.
While the veg fry, peel and crush or grate the garlic. Peel and grate the ginger. Stir them into the veg with 1 heaped tbsp Bombay spice blend, 1 tbsp black onion seeds and curry leaves. Cook and stir for 1 min.
Add the diced lamb to the pan and stir to mix, then pour in 300ml boiling water. Stir to mix well, pop on a lid (or use a baking tray if you don’t have a lid) and bring to the boil. Turn the heat down and simmer for 30 mins till the lamb is tender when pressed with a fork.
When the lamb is 15 mins away from being r eady, tip the rice into a sieve and rinse it under cold water. Tip into a small pan, add a pinch of salt and pour in 300ml boiling water. Cover and bring to the boil, then turn the heat right down and very gently simmer for 8 mins till the rice has absorbed all the water. Take off the heat and leave in the pan, lid on, for 3-5 mins to steam the rice and finish cooking it.
Fold the spinach into the curry to wilt it. Taste and add a pinch of salt if you think it needs it.
Fluff the rice with a fork and divide between a couple of warm plates. Top with the Bombay spiced lamb and serve.