In a large saucepan, combine mashed bananas, granulated sugar, brown sugar, lemon juice, ground cinnamon, ground nutmeg, salt, and water. Stir to mix well.
Place the saucepan over medium heat and bring the mixture to a boil, stirring frequently to prevent sticking.
Once boiling, reduce heat to medium-low and simmer for 5 minutes, stirring occasionally.
Gradually stir in the fruit pectin pouch, mixing thoroughly to avoid lumps.
Increase heat and bring the mixture back to a full rolling boil. Boil for exactly 1 minute while stirring constantly.
Remove the saucepan from heat and stir in the vanilla extract.
Skim off any foam from the surface using a spoon.
Pour the hot jam into sterilized jars, leaving 1/4 inch headspace at the top.
Wipe the rims of the jars clean and seal with sterilized lids and bands.
Allow the jars to cool to room temperature, then refrigerate. The jam will thicken as it cools.
Store refrigerated and consume within 3 weeks or process in a water bath canner for longer shelf life.