Set the Instant Pot to 'Sauté'. Add a drizzle of olive oil, and when it is hot add the onion, and sauté, stirring often until the onion is tender. Stir in the garlic and cook for around 30 seconds.
Add the tomato paste and stock to the Instant Pot bowl, and deglaze the bottom of the bowl [Note 1]. Press 'Cancel' to end the saute function.
Rinse the rice in a sieve until the water runs clear [Note 2].
Add the rice and seasonings (salt, cumin, and black pepper) to the Instant Pot bowl and stir.
Lock the lid onto the Instant Pot, and set to 'Manual' or 'Pressure Cook' for 7 minutes. Allow the pressure to release naturally.
Once the valve drops, open the pressure cooker and stir the rice to mix the sauce evenly through it, and to fluff up the grains, before serving.
Notes
Gently scrape with a wooden spoon to remove any cooked-on flavor.
Rinsing the rice removes excess starch and adds a little extra water to the rice. This prevents it from becoming gummy when cooked in a pressure cooker.