1. In a large heavy-bottomed pan, heat oil on medium-high for 1 minute. Add onion and sauté for about 8 minutes, or until light golden on the edges. (Don't overcook the red onion, as it is meant to give a sweeter taste to this curry.)
2. Add garlic and sauté for 2–3 minutes, then add tomatoes and stir well.
3. Add turmeric, cumin, chili powder, salt and cayenne and sauté for 5 minutes.
4. Stir in chicken, pour in water and bring to a boil. Reduce the heat to medium, cover and cook for 10 minutes.
5. Remove the lid carefully and stir in green beans. Cook, uncovered, for 5 minutes, or until beans are just slightly crunchy and chicken is cooked (74° C or 165° F).

Meeru and Vikram write,

Although this recipe calls for boneless thigh meat, you can just as easily use bone-in thigh (just make sure it's enough meat for six servings and add an extra cup of water so you can get a nice chicken broth in your curry)... Serve this dish with rice, couscous, pita bread, naan or even boiled potatoes.