Remove stems from fruits. Rinse lightly under cool water if there is dirt on them. Cut fruits in half along the short side (equator). Scoop seeds and pulp into a large mason jar or pitcher. Cover and store seeds and pulp in refrigerator.
Cover emptied out shells with filtered water and add a weight to keep shells submerged. Soak overnight.
Pour the soaking water and shells into a pot and bring to a boil, and simmer 45 to 60 minutes, or until the inner part of the shells becomes translucent.
Drain water from shells and let cool.
Scoop out insides of shells into a bowl. I find a regular teaspoon works best. Discard the outer paper husks. TIP: Make this a meditation; it takes patience and practice to remove the shells without tearing the outer husks.
Strain the reserved pulp and seeds through a mesh strainer to separate them from the juice. Reserve 1 cup (240 ml) of juice, and enjoy extra juice separately. TIP: Use the extra juice to flavor kombucha or water kefir! Or freeze it into ice cube trays for later use.
Add shells to a saucepot. Stir in sugar.
Squeeze lemon juice into the pot and blend to an applesauce consistency with an immersion blender. Add some of the freshly strained juice as needed to blend the mixture smoothly.
If using, mince hot pepper (remove seeds and white membrane for less heat, or leave for more heat) and add to mixture.
Cook mixture on medium-high heat. Keep stirring occasionally so it does not stick to bottom or burn, until jam thickens considerably, usually about 30 minutes. Temperature should be at or near boiling (212℉ / 100℃).
In a canning pot, add jars, lids, rings, tongs, and a canning funnel. Cover with water and bring to a boil 10-15 minutes to sterilize them.
Remove jam mixture from heat, add vanilla extract, strained pulp and reserved juice to mixture and stir well.
Remove sterilized jars from pot. Leave canning pot boiling, adding water as needed to cover 1 inch over the top of the tallest jar.
Carefully scoop or spoon jam into jars with canning funnel, leaving 1/4 to 1/2" (1/2 to 1 cm) space from the top rim of the jar.
Add lids and rings to the jars, and submerge in boiling water. Boil for 10-15 minutes.
Remove jars and let cool. Loosen rings on jars if using mason rings/jars. Jars will seal themselves as they cool. If any jars don't seal, store those in the refrigerator and consume them first.