01 - Combine chicken with yogurt, lemon juice, turmeric, and salt in a large bowl. Mix thoroughly to coat all pieces. Let marinate for at least 15 minutes, or up to 2 hours for deeper flavor penetration.
02 - Heat vegetable oil in a large skillet or Dutch oven over medium heat. Add chopped onions and cook for 5-7 minutes, stirring occasionally, until golden brown and softened.
03 - Add minced ginger, garlic, and chopped jalapeños to the skillet. Cook for 2-3 minutes, stirring constantly, until fragrant and raw garlic smell dissipates.
04 - Stir in diced tomatoes and continue cooking for 4-5 minutes. Cook until tomatoes soften and begin to break down, forming a base for the sauce.
05 - Sprinkle in coriander, cumin, garam masala, cinnamon, chili powder, and black pepper. Stir well to combine and cook for 1 minute to toast the spices and release their aromatic oils.
06 - Add marinated chicken pieces to the skillet. Cook, stirring frequently, for about 5 minutes until chicken is lightly browned on all sides.
07 - Pour in water or chicken broth, scraping up any browned bits from the bottom of the pan. Bring to a gentle simmer, cover, and cook for 15-20 minutes until chicken is cooked through and sauce has thickened to desired consistency.
08 - Taste the curry and adjust salt or heat level as needed. Transfer to serving bowls, garnish generously with chopped fresh cilantro, and serve hot alongside steamed basmati rice or warm naan bread.