Chop vegetables as per the size your like.
Make paste of onion, tomato, garlic, ginger and whole red chilli(optional).
In a pan heat oil, add the onion tomato paste, and saute till raw smell of onions and garlic goes away.
Mix garam masala, turmeric(optional) and red chilli powder if you are not using dry whole red chilli.
Add finely chopped vegetables, bell peppers first, then carrots and finely cabbage. Stir fry for few minutes and then add vegetable broth or water. Add salt and mix.
Add spinach at the end if using
Cook for few minutes until the soup boils. You can garnish with spring onion greens or fresh cilantro.