Choose a fully ripe, healthy tomato
Cut the tomato open
Scoop out the seed gel into a clean container
Add a small amount of water
Let the mixture ferment for 2 to 4 days at room temperature
Stir once a day
Wait until the seeds sink and mold forms on top
Add more water and swirl
Pour off the pulp and floating seeds
Repeat rinsing until only clean seeds remain
Spread the seeds on a paper towel, coffee filter, or screen
Dry the seeds completely for 1 to 2 weeks
Store the dried seeds in a labeled, airtight container
Keep the container in a cool, dry place