Rinse the lentils and drain them.
Select the Sauté setting on the Instant Pot and after a few minutes, add 1/2 tablespoon of the coconut oil, followed by the cumin seeds. Toss for 30-60 seconds until lightly browned and very fragrant.
Add the remaining 1 tablespoon oil, followed by the onion and 1/2 teaspoon of the kosher salt. Cook the onion for 4-5 minutes until lightly browned. Then add the garlic and ginger and cook for 1 minute, stirring frequently to prevent sticking.
Stir in the the curry powder, turmeric, and cayenne (if using) for 30 seconds, adding the 2 tbsp water to prevent the mixture from drying out too much.
Add the chopped butternut squash and stir to coat it in the spice mixture. Pour in the vegetable broth and use a wooden spoon or spatula to scrape up any browned bits at the bottom of the pan. Then add the remaining 1 teaspoon kosher salt, the lentils, and coconut milk. Scoop the cashew butter on top but do not stir. This helps prevent the nut butter from sinking to the bottom and possibly triggering the Instant Pot burn warning.
Secure the Instant Pot lid and set the Pressure Release to Sealing. Select the Pressure Cook or Manual setting and set the cook time for 10 minutes.
Once the timer goes off, allow a natural pressure release. Once the pressure has released, open the pot and stir in the baby kale. Select the Sauté setting and heat for about 2 minutes or until the kale has wilted, then select Cancel. Add the lemon or lime juice and the cilantro and stir to combine.
Serve the butternut squash lentil curry over white rice or with flatbread.