Preheat the instant pot by selecting the sauté setting.
Heat the oil in the preheated pot, then add the mustard seeds and leave for about 30 seconds, or until they start to splutter.
Add the onion, garlic, ginger, chili, and a pinch of salt and cook until the onion is translucent, about 2 minutes.
Add the spices and mix well. Add the tomatoes and a quarter cup of water and cook for 2 minutes stirring occasionally to avoid sticking.
Add the butternut squash or pumpkin, coconut milk, remaining 3/4 teaspoon of salt, and remaining 1/2 cup (120 ml) of water. Add the lentils to the pot, and give it a good stir to combine and scrape up any bits of tomato from the bottom of the pot.
Close the lid and pressure cook for 4 minutes. Carefully quick release the pressure slowly once cooking time is done.
Open the lid and fold in the spinach and mix thoroughly. Taste and adjust the amount of salt, heat, and flavor. Add a good dash of lime juice. Garnish with pepper flakes or cilantro. Serve over rice or vegan flat bread or with fresh dinner rolls.