In a small bowl, combine the garam masala, cumin, turmeric, smoked paprika, salt, cayenne, and some freshly cracked pepper (about 10 cranks of a pepper mill). Sprinkle the spice mix over both sides of the chicken breasts, coating them liberally.
Add olive oil to Instant Pot, and saute onions and garlic for 8 minutes.
Combine remaining ingredients (except heavy cream) to the Instant Pot. Cook for 10 minutes on high pressure.
Quick release, then add the heavy cream. Stir gently to combine the cream with the tomato sauce. Taste the sauce and add salt if needed.