Cut the pumpkin or squash in half. Remove the pumpkin seeds and set aside on a paper towel. Cube the rest of the squash into medium cubes. Smaller pieces will make for easier roasting.
Turn the oven to 375 F, and place the squash or pumpkin cubes on a baking tray lined with parchment paper (or oiled).
Put the squash in the preheated oven for an hour to roast. It should be very soft and able to be easily pricked by a fork when it's done (about 30-40 minutes).
Once the squash is ready, warm up a large pot on the stove to medium heat.
Add the oil. Once it's hot, add in the onion, garlic, and ginger. Sautee until the onions are tender, for a couple minutes.
Add in the butternut squash, and sautee this for another couple minutes.
Then add in the rest of the ingredients (as well as the cayenne and thyme, if using). Turn the heat to medium-low for about 20 minutes, until the lentils are very soft.
Once the lentils are soft and able to be squished easily, use a handheld blender to blend together the squash mixture until it is a soup. If fresh thyme is in the pot, then remove it before blending.
Bring the mixture to a boil by turning the heat to high, constantly stirring.
Once this boils, remove it from the heat.
Pour into serving dishes and serve warm, topping with the optional ingredients listed above.