One of the reasons berries work well is because, they are small so slicing them isn't needed. But just like with strawberries, you can also use sliced fruit such as kiwi, apple and pears. Mandarin oranges are also beautiful and taste great with all the other flavors, but because they are packed in water, be sure to rinse them well and gently pat them dry with paper towels to remove all the excess moisture. You'll want to avoid using super watery fruits like watermelon. The water content makes the tarts too soggy.