In a large saucepan, combine the pumpkin purée, apple cider, sugar, maple syrup, lemon juice, pumpkin pie spice, and salt. Bring to a boil over medium-high heat, stirring regularly.
Once it reaches a boil, reduce the heat to low and cover the saucepan.
Stir regularly to keep the pumpkin butter from sticking or burning, and continue to cook until thickened. This will take about 20-25 minutes.
Remove from heat, and let it cool completely.
Once cool, transfer to an airtight container and store in the refrigerator.
Notes
Pumpkin purée: Be sure to use canned pumpkin purée, not pumpkin pie filling.