Place pumpkin puree, apple cider vinegar, maple syrup, brown sugar, apple juice, and pumpkin pie spice in a large saucepan over medium-high heat and bring to a low boil, stirring constantly.
Reduce heat to low and simmer for 20 minutes. Stir frequently.
Remove from burner and stir in vanilla. Cool completely then transfer to a jar with a tight-fitting lid.
Recipe by Premeditated Leftovers™ at https://premeditatedleftovers.com/?p=31311