Turn on the Instant Pot and select sauté mode.
Heat oil and add chopped onions; sauté until soft.
Add garlic and cook for a minute.
Add chopped sweet potatoes and mix well.
Add red lentils, turmeric, and other spices.
Pour in water or vegetable broth and stir.
Close the lid and cook on high pressure for 10 minutes.
Allow natural pressure release for 10 minutes.
Open the lid and blend the soup for a smooth consistency (optional).
Adjust salt and garnish with fresh herbs before serving.