Combine water and sugar in a small saucepan over medium heat. Stir until the sugar dissolves and the mixture comes to a simmer.
¼ cup brown sugar, ¼ cup granulated sugar, ½ cup water
Reduce the heat to medium-low then add in the sweetened condensed milk, pumpkin puree, pumpkin pie spice, and salt. Stir to combine.
⅔ cup pumpkin puree, 14 oz sweetened condensed milk, ¾ teaspoon pumpkin pie spice, ¼ teaspoon salt
Bring the mixture to a boil, then reduce to simmer and allow it to simmer for 3 minutes.
Remove from the heat, add in the vanilla extract, and mix again. Allow the sauce to cool down a little before adding it to a jar. Cool down fully before chilling in the fridge.
1 teaspoon vanilla extract