Place pumpkin and water in a saucepan. Bring to a boil, reduce heat to low and simmer until the pumpkin has broken down. Strain through a strainer or food mill. If using canned pumpkin, omit this step and pick up below. Combine pumpkin puree with sugar and spices, and choose one of the following cooking methods.
Slow Cooker: Place sweetened pulp in a slow cooker with lid partially off to let steam escape. Set at low and cook, stirring occasionally, for 6-12 hours or overnight, or until thick enough so the butter doesn't run off a spoon when turned upside down.
Microwave: Place sweetened pulp in a microwave-safe bowl and cook for 20 minutes at a time, stirring frequently until thick enough so the butter doesn't run off a spoon when turned upside down.
Stovetop: Place sweetened pulp in a medium saucepan and cook over medium-low heat, stirring frequently, for 1-2 hours or until thick enough so the butter doesn't run off a spoon when turned upside down.
Oven: Heat oven to 250°. Place sweetened pulp in a heatproof casserole dish or roaster. Bake, stirring only occasionally, for 1-3 hours or until thick enough so the butter doesn't run off a spoon when turned upside down.
