Heat a pan over medium heat. Add 2 tablespoons oil and onion. Saute onion until translucent about 7 minutes then add garlic and cook for 1 minute.
Mix chili powder and turmeric in a small bowl. Season chicken with salt then coat chicken with the chili powder mixture. Heat a large cast iron pan to medium high heat and add the remaining oil. Sear the chicken until golden brown about 12 minutes. Stir in the onion mixture, tomatoes, cumin, ginger, water, and coriander. Reduce heat, cover and simmer for about 25 minutes stirring few times.. Add the lemon juice and butter and cook for another 5 minutes. Add more water if it becomes too dry. Garnish with fresh cilantro and red chili.
Recipe by The Gluten Free at https://www.theglutenfree.com/gluten-free-chicken-jalfrezi/