Heat a non-stick skillet over medium heat and lightly coat with cooking spray or butter.
Place one flour tortilla in the skillet.
Spread half of the shredded or sliced mozzarella cheese evenly over the tortilla.
Arrange the tomato slices evenly over the cheese.
Distribute the fresh basil leaves evenly over the tomatoes.
Add the remaining mozzarella cheese on top of the basil leaves.
Cover with the second flour tortilla.
Cook until the bottom tortilla is golden brown and the cheese is melted, about 3-4 minutes.
Carefully flip the quesadilla using a spatula, and cook the other side until golden brown, about 2-3 minutes.
Remove from the skillet and let it cool for a minute before cutting into wedges.
Pack in a lunchbox with a side of balsamic glaze for dipping.