Combine water, tomatoes, coconut milk, red lentils, spinach, onion, tomato paste, curry powder, garlic, bouillon base, and cayenne pepper in a multi-functional pressure cooker (such as Instant Pot®). Close and lock the lid.

Select high pressure according to manufacturer's instructions; set timer for 15 minutes. Allow 10 to 15 minutes for pressure to build.

Release pressure using the natural-release method according to manufacturer's instructions, about 10 minutes. Unlock and remove the lid. Stir and let sit for 5 minutes before serving.