Preheat the oven to 375Place parchment paper on a sheet pan and brush olive oil across the parchment paper.
Cut the squash in half (lengthwise), scoop out the seeds. Rinse the seeds to remove stringy squash, pat dry, sprinkle with salt. Lay the squash, face down, on an olive oil brushed baking sheet with the seeds on the side. Roast the seeds until they smell nutty, about 15-minutes, and the squash until tender, about 45-minutes.
While the squash is roasting, place the lentils, water, garlic, chilies and orange rind in a medium saucepan with a lid. Simmer until the lentils are soft and have absorbed most of the water, about 20-minutes. Cool.
Cool the seeds and grind them, setting aside to add later. Cool the squash and carefully scoop out the tender flesh, reserving the butternut shell, should you want to serve the hummus in the shell.
Transfer the cooled squash and cooled lentil mixture (rinds and all), to a processor or blender, and add the sumac, tahini and salt. Puree until creamy. Serve with the prepared seeds on top.