Cut cucumber in half lengthwise. Use a spoon (I like to use a baby spoon without a sharp edge) to gently scrape out all the seeds.
Rinse the seeds, then place into a cup of water for 3 - 4 days to allow them to ferment slightly.
Cut the tomato into slices and squeeze the centers of the fruit into a dish. Leave dish to dry. Damp is the enemy of tomato seeds.