Marinate the chicken: In a bowl, mix yogurt, lemon juice, 1 tsp garam masala, turmeric, cumin, chili powder, ginger paste, garlic paste, and salt. Add chicken pieces and coat well. Cover and refrigerate for at least 1 hour, preferably overnight.

Cook the chicken: Heat a large pan over medium-high heat. Add a little oil and cook the marinated chicken pieces until lightly browned but not fully cooked, about 5-6 minutes. Remove and set aside.

Prepare the sauce: In the same pan, melt butter. Add chopped onions and sauté until golden brown, about 5 minutes. Add remaining 1 tsp garam masala and stir for 30 seconds until fragrant.

Add tomato puree to the onions and cook for 5 minutes, stirring occasionally. Then add sugar and salt to taste. Cook for another 2-3 minutes.

Blend the sauce: Let the mixture cool slightly, then transfer to a blender and blend until smooth. Return to the pan.

Finish the dish: Add the partially cooked chicken pieces to the sauce. Stir in heavy cream and fenugreek leaves. Simmer on low heat for 10-15 minutes until chicken is fully cooked and sauce thickens.

Garnish with fresh cilantro and serve hot with naan or steamed rice.