Stephen, that looks pretty nice. I have eaten vegetable Nentara before and recall enjoying it. Have you thought of adding the tomato by the inclusion of either a Makhani Gravy (Butter Sauce) or a Masala Sauce. Both of these are very Indian in style and flavour but rich in tomato. I have recently had some very pleasing results using hybrids of these sauces with base gravy. The ratios of each can give a lot of control as to the scale of tomato depth.
I used Mridula Baljekar's "The Real Balti" Makhani Gravy which is good. I believe Chewytikka has a Masala Sauce video or there is a recipe in J & P L:ardner's Balti book. I'm sure you wont struggle to find a good Indian Tomato sauce.
Of course it may be something as simple as using Campbell's Tomato Soup concentrate which I understand was common in BIR kitchens for that authentic taste.
