Preheat the oven to 375 degrees C (190 degrees C).
Thinly slice chicken breasts in half and season with Italian seasoning and salt. Place chicken on a rimmed baking sheet.
Bake in the preheated oven until chicken is no longer pink in the center and the juices run clear, about 20 minutes. An instant read thermometer inserted into the center should read at least 165 degrees F (74 degrees C).
Cut heirloom tomato and mozzarella cheese into four 1/3 inch thick slices. Set out tomato slices on a baking sheet and top with mozzarella slices. Add to oven and bake for the last 10 minutes with the chicken. Remove chicken from oven.
Turn oven to broil and broil tomatoes and cheese, until cheese has melted, 2 to 3 minutes. If desired, add ciabatta buns and toast under the broiler until browned, 1 to 2 minutes.
To assemble the sandwiches, place a chicken filet onto the ciabatta bun, top with tomato and melted mozzarella, and 1 tablespoon pesto.
Pesto Chicken Caprese Sandwich · Dinner Match Lab | Dinner Match Lab