In a large bowl, combine the tomatoes, horseradish, tamari, and salt. Take one of the garlic cloves and finely grate it with a Mircroplane into the bowl. You could also mince it very finely with a knife and just add it to the tomatoes after. Toss the tomatoes to combine. Let the tomatoes sit for 30 minutes.
While the tomatoes are marinating, in a medium bowl, combine celery, red onion, parsley, and olive oil. Toss to coat evenly and set aside.
Once the tomatoes have marinated for 30 minutes, strain all of the accumulated juice into a small skillet or saucepan. There should be about ¼ - ⅓ cup of liquid. Place the skillet/saucepan over medium heat on the stove and bring to a simmer. Reduce the tomato juice mixture down to roughly 2 tablespoons and remove from the heat. Set aside.
Grill, broil, or toast the ciabatta until golden and crispy. Cut the toasted ciabatta into 12 even pieces. Cut the remaining garlic clove in half crosswise. Rub the cut surfaces of the ciabatta pieces with the garlic clove and then place on a platter.
Lightly brush each piece of ciabatta with the reduced tomato mixture. Then, spoon the tomatoes onto each piece of ciabatta. Top each bruschetta with a little tangle of the celery/onion/parsley salad. From here you can top the bloody Mary bruschetta with whatever garnishes you like. I went with pepperoncini peppers, olives, and vegan “parmesan.” Enjoy immediately!