Start by marinating the chicken to ensure it absorbs all the lovely flavors. Combine the chicken pieces with lemon juice, salt, black pepper, and red chili powder in a bowl. Toss to coat, then let the chicken rest for 15–20 minutes. While it marinates, prep your veggies.
Heat oil in your pan or wok over medium heat. Add the onions and sauté until golden brown, stirring occasionally to avoid burning. Stir in the ginger and garlic paste, cooking until fragrant. Add the marinated chicken and cook until it turns white on the outside, about 4–5 minutes.
Sprinkle over the cumin, coriander, garam masala, and turmeric. Stir well, so the spices coat the chicken evenly. Pour in the tomato puree, and cook until you see the oil separating from the sauce. This step makes all the difference in the richness of the curry.
Meanwhile, heat a little more oil in a separate pan. Add the sliced green chili and bell peppers, stirring over high heat for 3–4 minutes. You want them slightly tender but still crunchy. Toss in the diced onions last, so they keep their shape.
Add the stir-fried vegetables and kasuri methi to the chicken mixture. Stir gently to combine everything without breaking up the vegetables. Taste and adjust seasoning, then cook for a couple more minutes until the dish is perfectly heated through.
Remove from heat and garnish with fresh cilantro if desired. Serve hot with your favorite sides.