Tahini is not a traditional ingredient in Indian dishes, but here it adds a richness normally provided by cream. If you’re avoiding all added fat, you can leave it out.
You can use spinach or another green instead of kale, but measure it by weight, not cups.
If you would like a smoother texture, process the kale/tomato/onion mixture briefly in the food processor after step 2. Return it to the pan before adding the chickpeas and continuing the recipe.