Dice tomatoes into ¼-inch cubes. Place in a fine mesh strainer over a bowl and sprinkle with ¼ teaspoon salt to draw out excess moisture. Let sit for 15 minutes.

Transfer drained tomatoes to a mixing bowl, add minced garlic, basil, olive oil, balsamic vinegar, and black pepper. Gently fold to combine. Cover and refrigerate for at least 30 minutes to allow flavors to develop.

Place chicken breasts between two sheets of plastic wrap or parchment paper. Using a meat mallet or rolling pin, gently pound to an even ¾-inch thickness. Pat dry with paper towels.

Combine salt, pepper, garlic powder, and dried oregano in a small bowl. Brush chicken breasts with 1 tablespoon olive oil, then apply seasoning mixture evenly to both sides of each breast.

Heat remaining tablespoon of olive oil in a heavy-bottomed skillet over medium-high heat until shimmering. Add chicken breasts and sear for 5-7 minutes on the first side until golden brown.

Flip and continue cooking for 4-6 minutes more until internal temperature reaches 165°F at the thickest part.

While chicken cooks, combine balsamic vinegar and sweetener in a small saucepan over medium heat. Bring to a simmer, then reduce heat to medium-low and cook until reduced by about half and mixture coats the back of a spoon (approximately 5-7 minutes). Remove from heat.

Transfer cooked chicken to a clean cutting board and allow to rest for 3-5 minutes to redistribute juices.

Give the bruschetta mixture a final stir, then spoon generously over each chicken breast. Drizzle with balsamic glaze if using. Serve immediately.