Puree the onion, chili and water in a blender until a loose paste is formed.
In a dutch oven over medium heat, melt the ghee and pour in the onion puree. Bring to a boil, turn heat to low and simmer for 15-18 minutes, or until it turns a dark golden brown and thickens to a paste, stirring often.
Turn the heat to medium and add the ginger and garlic, stirring to cook for 2 minutes.
Add the tomato passata, garam masala, cumin and fenugreek leaves. Stir in the beans and the liquid, season with salt and bring to a boil. Turn heat to low and simmer 10 minutes.
Serve with chopped cilantro on top. I like this with warm naan and steamed rice.
Notes
I use canned kidney beans and their liquid. If you want to make beans from scratch, use 3 1/2 cups dried, soaked and cooked kidney beans along with 1 cup of cooking liquid.
This recipe was previously published on my other food site, Kevin Is Cooking, as Red Kidney Bean Curry with Lamb, dated March 2014. I have since updated the cooking technique and omitted ground lamb from the recipe.