Make 2 to 3 slits in the chicken breasts. Apply salt and lemon juice to the chicken breasts. Mix yogurt, red chili powder, garam masala, ginger, and garlic. Apply evenly to the chicken breasts and allow to marinate for 20 minutes or refrigerate if marinating ahead of time. Marinating chicken for 4-5 hours or overnight works well.
Set the Instant Pot to Saute mode and heat butter or oil. Add onions and saute for 2 minutes. Add ginger, garlic and mix well. Add tomatoes, turmeric, salt red chili powder, and garam masala. Mix well. Press Cancel. Add 2 tablespoons of water. Deglaze the pot if needed.
Place the tall trivet in the main pot. Place the marinated chicken over the trivet. Baste the chicken with oil. Close the Instant Pot with the pressure valve to sealing. Pressure Cook for 8 minutes followed by 10-minute natural pressure release.
Open the Instant Pot. Take the chicken and the trivet out. Using an immersion blender, blend the sauce until smooth and bring the sauce to boil on saute mode.
Stir in cream, fenugreek leaves, and sugar. Note the optional step is to broil the cooked chicken for 5 minutes to get some char marks. Cut the chicken into 2-inch pieces and add them to the sauce. Set the Instant Pot to saute mode and bring the sauce to a gentle boil. The sauce will thicken further as it cools down. Garnish with cilantro.
Use plain full fat or greek yogurt for the marinade
Pat dry the chicken to avoid extra liquids in the marinade
Discard any leftover marinade or brush it on the chicken for spicier curry
1 cup of pureed tomatoes can be substituted for fresh tomatoes