Quarter the vine tomatoes and shred the shallots, garlic and cilantro. Put everything in a bowl, pour over some lime juice and add the fleur de sel.

Then go wash your hands thoroughly first, because now the fun part begins: knead everything well with your hands until the vegetables release their moisture. This takes 3 to 5 minutes.

Then put the mixture into the glass jar. It may not even be half full, but that's just the point. Make a fist and press the tomatoes well so that there are no more air bubbles. Put the plastic bag in the jar and fill it with water. This way, no air can get to the tomatoes; this is what you might call a "water lock. Put a couple of towels over the jar and set it aside at room temperature. After 3 days, your fermentation will be complete.

Now transfer the contents to a smaller jar, filling it to the top so that little air can reach it. Seal the jar hermetically with a lid. From then on, do store the jar in the refrigerator. Then the fermentation process stops and the contents (sealed) will keep for at least a few months. The result is a slightly sour sauce, but with a delicious taste.

TIP - FERMENTING
I readily admit that fermentation is really something for enthusiasts. I myself discovered it not so long ago, and I have delved into it with enthusiasm. Everyone should give it a try. It's just fun and exciting to follow the fermentation process.

In the beginning it may take some searching and you may not dare to start.
On the Internet (e.g. YouTube) you will find a lot of information and videos that can help you get started.
It is more the fear of doing something wrong that keeps most from doing it, but it is really not difficult. Think of fermented vegetables as extra flavoring. Eat them occasionally and think of them as an addition to a richly varied diet, as part of a meal.

TIP - HYGIENE IS IMPORTANT
Fermentation is nothing but a controlled rotting process. But we only want the good bacteria to do this, which is why it is necessary to always be hygienic and wash the jars you use out well first. Put them in the dishwasher or wash and rinse them well by hand. The Dutch Nutrition Center considers eating fermented foods to be safe.

TIP - READING MATERIAL ON FERMENTATION
If you want to learn more about fermenting foods, I recommend the book The Art of Fermentation by Sandor Ellix Katz (Chelsea Green Publishing, 2012).
An absolute must on how the gut works is The Beautiful Food Machine by young German author Giulia Enders (Luitingh-Sijthoff, 2015). Everyone should read that book to gain a greater understanding and respect for the wondrous and ingenious workings of our gut. It is a science-based book, but also very readable and written with a lot of humor.

Find more info on good gut bacteria, here or in Pure Food 2.