Begin by prepping the topping. Combine tomatoes, red onion, garlic, and basil in a medium bowl. Add balsamic vinegar and extra virgin olive oil and mix. Sprinkle with kosher salt until seasoned to taste. Set aside and let it marinate until needed.
Preheat oven to Broil or if no broil setting is available, 425F. Place baguette slices on a baking sheet covered in foil and drizzle with extra virgin olive oil. Broil in the oven for 4-5 minutes or until lightly browned.
Rub each slice with the clove of garlic and then top each slice with a spoonful of the bruschetta topping and mozzarella cheese. Serve and enjoy!