In a large bowl combine pork, onion, salt and pepper. Cover the bowl with a plastic wrap or lid and marinate for 2 hours or overnight*. (See the note 2)
If you use the wood skewers, make sure to soak them in water for a minimum of 30 minutes before grilling. This will keep them from burning up on the grill.
Thread the meat, sliced zucchini and tomatoes onto the skewers.
Preheat the grill to a medium high heat.
Grill for 15-20 minutes turning from time to time, until Shashlik is brown on the sides and cooked through. (After 15 minutes, remove one piece of Shashlik from the skewer and slice in half. If it’s no longer pink in the centre, Shashlik is ready.)
To make Shashlik Sauce
In a blender or food processor combine all ingredients for the sauce and process until creamy. Serve immediately with Shashlik.
Note 1I recommend grating the onion on a large or small grater. You can also use a Kitchen Aid meat grinder attachment. Alternatively, you can thinly slice the onion. But I believe that grating the onion releases more juice making it easier to penetrate into the meat.Note 2Despite that traditionally Georgians don’t marinate meat before grilling, we still like to do so. 2 hours should be enough for the onion to infuse the meat with a flavor.