If you can find kumquats, I suggest you give them a try. They’re tart and sweet citrus fruits with tender skins that you eat. They’re a sunshiney delight! However, I know they may not always be available. In this case, you can use peeled segments of mandarins, clementines, sweet oranges, or, if you can find them, calamansi. Otherwise, consider substituting in season berries.