01 - Combine chicken pieces with yogurt, lemon juice, turmeric, and salt in a large bowl. Mix thoroughly to coat all pieces. Marinate for at least 15 minutes, or up to 2 hours for enhanced flavor penetration.
02 - Heat vegetable oil in a large skillet or Dutch oven over medium heat. Add finely 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. Sauté for 2-3 minutes, stirring constantly, until fragrant and raw aromas dissipate.
04 - Stir in diced tomatoes and continue cooking for 4-5 minutes. Cook until tomatoes soften completely and begin to break down, forming a base for the sauce.
05 - Sprinkle coriander, cumin, garam masala, cinnamon, chili powder, and black pepper evenly over the mixture. Stir well and cook for 1 minute to toast the spices and release their essential oils.
06 - Add marinated chicken pieces to the pot, discarding excess marinade if needed. Cook for 5 minutes, stirring frequently, until chicken develops a light golden-brown exterior.
07 - Pour in water or chicken broth, scraping the bottom of the pot to incorporate browned bits. Bring to a gentle simmer, cover, and cook for 15-20 minutes until chicken is cooked through and sauce reaches 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 immediately with steamed basmati rice or warm naan bread.