Preheat the oven to 425°. Wrap the sweet potato in aluminum foil and place on a baking tray. Bake in the oven for 30-40 minutes, or until soft. Remove from the oven and let cool. Once cool enough to handle, remove the foil and scoop out the tender flesh. Discard the skin.
Add the sweet potato, chickpeas, tahini, olive oil, fresh lemon juice, garlic, salt and cayenne to a food processor or high-powered blender. Pulse until everything is combined then add water 1 tablespoon at a time, until the hummus is a smooth, thick and spreadable consistency. Taste and add more salt if necessary.