Set the Instant Pot to sauté mode and add the olive oil. Once hot, cook the onion for 3 minutes until it softens.
Stir in the garlic and ginger and cook for 1 minute more until fragrant.
Add the sweet potatoes, lentils, diced tomatoes, vegetable broth, cumin, salt, and pepper. Stir to combine.
Secure the lid, set the valve to sealing, and cook on high pressure for 12 minutes.
Allow a natural pressure release for 10 minutes, then quick release any remaining pressure.
Open the lid, stir the stew, and adjust salt if needed. Serve hot with fresh cilantro on top.