Heat the avocado oil using the Sauté setting of the Instant Pot. For stovetop preparation, warm the oil in a pan over medium heat.
Add the chopped yellow onion, minced ginger, garlic, and deseeded jalapeño. Sauté for approximately 3 minutes, stirring from time to time, until the onion has softened and the aromatics become fragrant.
Stir the red curry paste into the sautéed mixture. Continue mixing until the paste is thoroughly distributed and releases its aroma.
Add the cubed butternut squash and split red lentils. Stir carefully so the squash and lentils are evenly coated with the curry mixture.
Season with the coriander, turmeric, smoked paprika, brown sugar, and salt. Mix until the seasonings are evenly incorporated.
Pour in 1 cup of water. Stir thoroughly while scraping across the bottom of the pot to loosen any ingredients that may have adhered to the surface.
For the Instant Pot method, secure the lid and move the valve to the sealing position. Cook on High Pressure for 4 minutes, then perform a quick pressure release when the cooking cycle is complete.
For the stovetop method, reduce the temperature to medium-low, cover the pan, and simmer for approximately 15–18 minutes, or until the butternut squash is tender and the lentils are fully cooked.
Once the pressure has been released, open the Instant Pot and select the Sauté function again. If using the stovetop method, increase the heat after the squash and lentils have finished cooking.
Stir in approximately 3/4 of the can of coconut milk. More coconut milk may be incorporated if a richer, creamier consistency is preferred.
Add the freshly squeezed lime juice along with fresh cilantro leaves. Stir gently to distribute them throughout the curry.
Allow the curry to simmer for another 2–3 minutes, giving the coconut milk, lime, spices, and aromatics time to blend together.
Serve the butternut squash curry hot and finish with additional fresh cilantro leaves as a garnish, if desired. Pair with steamed rice or another preferred grain.