Preheat a cast iron grill pan on medium high flame.
Slice the bread into 1 inch thick slices and grill it on both sides until nice dark grill marks forms. (If you don't have a grill pan just use a plain cast iron skillet instead).
Take a garlic clove and rub both sides of each side of the grilled bread to your taste. Use a pastry brush to dip in the olive oil and lightly brush both sides of the bruschetta. Sprinkle with sea salt all over and allow to cool.
Meanwhile slice your tomatoes into 1 inch pieces and the red onion into thin slices. Add them to a large salad bowl.
Use your hands and tear the bruschetta into 1 inch pieces on top of the tomatoes and onion.
Whisk together the remaining olive oil and red wine vinegar. Season to taste with a little sea salt then pour it over the bread and tomatoes. Add the capers and basil leaves and give everything a good toss to coat.
Taste and adjust seasonings with sea salt. Allow the panzanella salad to sit at room temperature for 20 minutes or so before serving.