Preheat your oven to 425°F. Set an oven rack to the lowest position. Line a large, rimmed baking sheet with high-heat-resistant parchment paper.
Wash and dry the pumpkin. Microwave it for one minute on high to soften.
Carefully, using a very sharp chef’s knife and back-and-forth sawing motions, cut the pumpkin in half. Slice a sliver from the stem side first if you don’t want to cut through the stem, which is difficult to do.
Use a large metal spoon to remove the pulp and the seeds. If some stubborn pulp remains, cut it with kitchen scissors. If desired, save the seeds to make roasted pumpkin seeds.
Back to using the sharp knife and the sawing motions, cut each pumpkin half into four one-inch-thick moon-shaped slices, discarding the ends.
Using a vegetable peeler, peel the skin off, then cut each pumpkin slice into 1-inch cubes.
Place the pumpkin cubes in a large bowl. Add the olive oil, kosher salt, garlic powder, and chili powder. Use a large spoon or your hands to evenly coat the pumpkin chunks.
Arrange the pumpkin cubes in a single layer on the prepared baking sheet. Bake them until tender, about 30 minutes, tossing them halfway through. Serve immediately.
Video
Notes
It's best to use a small sugar pumpkin when making this recipe. The bigger the pumpkin, the less flavor it has. You want a small pumpkin with firm, deep orange flesh. It's best to use the big pumpkins for Jack-o-lanterns, not for cooking.
If your sugar pumpkin is larger than 2 pounds, you'll need to microwave it for longer. In the video above, I used a 5-pound pumpkin and microwaved it for two minutes on each side.
Another option, shown in the video, is to skip the peeling, slicing, and cubing. Simply cut the pumpkin in half, remove the pulp and seeds, and place it cut-side-down on a parchment-lined rimmed baking sheet. Roast the pumpkin until fork-tender, about 30 minutes at 425°F. The result is not so much a side dish as a cooked pumpkin that you can mash and use in other recipes.
You can keep the leftovers in the fridge, in an airtight container, for 3-4 days. Reheat them gently in the microwave at 50% power. You can freeze the leftovers in freezer-safe containers or bags for up to three months.