Heat oil in a large frying pan on medium high heat. Sauté onion and garlic for 5 minutes. Stir in chilli powder and cumin, and cook 1 minute. Stir in tomato, rajmah and salt. Bring to the boil, then reduce heat and simmer for 20 minutes.
Stir in spinach and cook 5 minutes more. Spoon 1/4 of the mixture into the middle of a warm chapati. Wrap and garnish with avocado, soured cream and salsa.