Turn the Instant Pot to Saute, and add the olive oil to the pot. Season chicken with salt and pepper and sear in the Instant Pot until golden brown. Remove and set on a plate.
Add onion and smashed garlic cloves to the Pot and saute until soft and translucent. Add tomato paste and stir for two minutes. Add chopped tomatoes, chicken broth, thyme, olives, and capers.
Return the chicken to the Instant Pot, lock the lid, and set the "Manual" or "Pressure Cook" setting for 25 minutes.
Release pressure manually, then remove the lid with care. Remove the chicken and set aside. Turn on the saute setting and simmer the sauce an additional 10 minutes, until the sauce reduced to about a pint. Add chopped parsley and lemon juice, then pour over chicken.
Serve over rice, pasta, or polenta.