Core the Roma tomatoes and dice them finely, ensuring to drain off any excess liquid. Transfer to a medium mixing bowl. Stack basil leaves, roll tightly, and slice thinly into chiffonade ribbons; add to the bowl with the tomatoes. Finely mince all garlic cloves. In a small dish, combine 1 tsp of the minced garlic with 3 Tbsp olive oil and set aside. Add the remaining garlic to the tomato mixture. Season the tomatoes with 2 Tbsp olive oil, 1 Tbsp balsamic vinegar, 1/2 tsp sea salt, and 1/4 tsp black pepper. Mix gently and allow the mixture to marinate for 30 minutes at room temperature.

Preheat the oven to 400°F and line a baking sheet with parchment paper. Slice the baguette diagonally into 1/2-inch thick slices. Arrange slices on the baking sheet and brush each side with the reserved garlic-infused olive oil. Sprinkle the tops with shredded parmesan cheese. Bake for 5 minutes at 400°F, then broil for 1–2 minutes until the edges become golden and crisp.

To serve, place the toasted baguette slices on a platter. Provide the tomato topping in a separate bowl. Just before serving, spoon the tomato mixture onto each toast and, if desired, finish with a drizzle of olive oil and balsamic glaze.