Well for mine I used half a tin of tomatoes and half a carton of pasata (because they were left over in the fridge) then I added a chopped onion and a chopped red pepper then I just basically threw in a load of herbs, spices and curry powder.
I think I put Madras curry powder in this one along with garlic, chilli, cumin, oh a splash of white wine vinegar, a touch of sweetner, errrm, mixed herbs and then just left it to reduce down to a thick sauce (about half an hour) and threw in a handful of coriander towards the end.
Hubby (who's a bit of a curry expert) said it tasted very much like a Rogan Josh
You can mix in some 0% greek yog at the end (off the heat) to make it creamier if you like.
HTH - sorry I don't have quantities etc, I just kept throwing bits in.
Jo x