Whisk all the ingredients together in a heavy-bottomed saucepan and place over medium-high heat.
2 cups pumpkin puree, 1/4 cup brown sugar, 1/4 cup maple sugar, 1 tsp ginger, 1 tsp cinnamon, 1/2 tsp nutmeg, 1/8 tsp allspice, 1/8 tsp cloves, 1/4 cup juice
Bring the mixture just to a boil and reduce to medium-low or low heat - just enough to keep it at a simmer.
Cook the mixture, stirring often, until the is thickened with a dark brown, shiny, caramelized appearance (about 20-30 minutes).
Transfer the pumpkin butter to a two cup glass jar (or 2 one cup glass jars) and allow to cool completely before storing in the refrigerator.
Notes
I strongly encourage using pumpkin juice (if you make your own puree you can reserve some of the juice when straining the puree, or you may be able to find a pumpkin juice blend in your grocery store), apple juice, or cider rather than water for the additional liquid in this recipe. While water will certainly work, Alton Brown frequently said that water doesn't bring anything to the party (in terms of flavor) and I always opt to add more flavor whenever I can.