01 - Combine chicken pieces 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, stirring occasionally, until golden and softened, about 5 to 7 minutes.
03 - Add minced ginger, garlic, and chopped jalapeños to the skillet. Cook for 2 to 3 minutes, stirring constantly, until fragrant and raw aroma dissipates.
04 - Stir in diced tomatoes and cook for 4 to 5 minutes until softened and beginning to break down, forming a chunky base for the sauce.
05 - Sprinkle coriander, cumin, garam masala, cinnamon, chili powder, and black pepper over the mixture. Stir well to combine and cook for 1 minute to toast the spices and release their essential oils.
06 - Add marinated chicken pieces to the pot, reserving any excess marinade. Cook, stirring frequently, until chicken is lightly browned on all sides, about 5 minutes.
07 - Pour in water or chicken broth, scraping up any browned bits from the bottom of the pot. Bring to a gentle simmer, cover, and cook for 15 to 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. Garnish generously with chopped fresh cilantro and serve hot with steamed basmati rice or warm naan bread.