Grind all the ingredients mentioned under masala to a smooth paste in a blender using as little water and keep the paste aside.
Heat oil in a heavy bottomed pan, add onions and saute until onions turn translucent.
Add the masala paste and stir on medium low heat until all the moisture from the paste evaporates and the paste dries, add tomatoes and stir until the tomatoes turn soft and mushy.
Add all the vegetables, chili powder, salt to taste and water as required and allow to simmer until the vegetables are cooked, yet not mushy.
Adjust water as required to achieve required consistency, adjust salt and chili powder to taste and add garam masala and allow the curry to simmer until the flavors mingle.
Remove from heat and serve hot on a bed of plain steamed rice.