Prep your cukes! If using English cucumbers, I like to leave the skin on, but if using regular cucumbers, I peel about half of the tough skin. Chop the cucumbers into small chunks and set aside to drain on a paper towel for about 5 minutes (this step is optional).
Using a sharp knife, cut away the top stem of the tomatoes and scoop out the seeds with a spoon or melon baller. (I always save this! I usually put it into my freezer bag for making stock, but you can also save it for sauces, or to mix with eggs!) I definitely recommend fresh, juicy, in-season tomatoes for this.
Mix drained cucumbers with crumbled feta cheese, fresh basil, balsamic vinegar, and pepper. Stuff the cucumber mixture into the tomatoes and serve!
Note: Also, if you get lazy sometimes (like me), I recommend skipping the stuffing step and just tossing in some cherry tomatoes. Serve it over mixed greens or spinach and it is a super tasty salad.