Set your Instant Pot to saute and add oil.
Saute onions and garlic until translucent.
Stir in carrots, tomatoes, broth, and basil.
Season generously with salt and black pepper.
Turn off the saute feature, return the lid to the Instant Pot with the knob turned to seal, and cook on the "Soup" setting for 15 minutes.
Once the cooking time is complete, quick-release the pressure. Once pressure is fully released, remove the lid.
Carefully transfer the soup to a blender or use an immersion blender to blend the soup until smooth. If using a blender, return pureed soup to the pot.
With the Instant Pot on “warm,” stir in the heavy cream.
Serve immediately.