Press Sauté—normal/medium on the Instant Pot and heat the oil. Add the onion, garlic, serrano chiles, cumin, and pepper and cook, stirring constantly, for about 1 minute, until slightly softened. Add the broth and flour and stir until well combined. Press Cancel. Add the cream cheese, Cheddar cheese, Jack cheese, and tomato and stir until the cheeses melt.