Season lamb with salt and pepper. Add vinegar and toss to coat. Set aside to marinate.

Core your tomatoes, cut them in quarters and pop them in a blender. Process until completely liquid. You might have to add about ¼-1/2 cup of water to get them moving.

In a large skillet over a medium high heat, brown the lamb in batches, and remove to plate.

Add the sliced onion to pan and cook for a few minutes, until softened.

Now add in the garlic and chili peppers and stir.

Add in the curry paste. Stir and fry for a few more minutes.

Put lamb back in the pan, along with any juices that accumulated. Stir well to cover the lamb with the curry paste, onions and garlic.

Pour in the puréed fresh tomatoes. Stir well. Bring to the boil then reduce the fire to a slow simmer.

Cook covered for 45 minutes or until the lamb is tender, stirring occasionally.

Remove the lid and simmer until the liquid has reduced by half, so the sauce is thick and concentrated. This could take another 10-15 minutes. Taste for salt and add more if necessary.

Finish by stirring through the plain yogurt and chopped cilantro. Garnish with a dollop more of the yogurt and cilantro, if deserved.

Serve with rice or naan.