Ripe apple

 is a quest item in the and can be found during the main quest, The Beast of Toussaint.

After approaching the "unicorn" you need something to lure it and this, along with the Fragrant cake and Basket of carrots, can be looted from the various picnics nearby. This will work, as well as the carrots (or by using Axii, though that'll lead to a fight with other participants).

Associated quest

 * The Beast of Toussaint