Combine the first 10 ingredients (through cayenne pepper) in a 6-quart Instant Pot. Cover the cooker with the lid, and lock the lid in place. Turn the steam release handle to the SEALING position. Select the MANUAL/PRESSURE COOK setting. Select HIGH pressure for 6 minutes.
Let the pressure release naturally 15 minutes. Then carefully turn the steam release handle to the VENTING position, and let any additional steam fully escape (the float valve will drop). Remove the lid from the cooker. If desired, reserve a few vegetable pieces for garnish. Using a handheld immersion blender, blend the remaining soup mixture until smooth. Stir in the coconut milk. If desired, garnish with the reserved vegetables and cilantro.