The purple yam, commonly known as ube, is a type of yam commonly eaten as a dessert ingredient in Filipino cuisine. They make ube cake, ube donuts, ube cheesecake, and even ube donuts:
There's something about our new Ube Coconut Swirl on a Friday >>> 💜🥥🍥 pic.twitter.com/ToTPBmHnKh— Baskin-Robbins (@BaskinRobbins) April 15, 2022
This is odd since, being a yam, it is a type of tuber, not a fruit. This is the botanical definition of fruit based on the fact that ube don’t contain seeds.
However, part of being a culinary fruit is still that something is the botanical “fruit” of the plant, so ube are vegetables even though they are used in desserts. This is normally one of the hallmarks of being a fruit, but it’s not a definitive test. Sweet potatoes and pumpkins are other good examples of vegetables commonly being used in desserts. The other aspects of being a fruit like juiciness, sweetness, and such must also be considered. You would never grab a raw yam and bite into it for a snack.
Purple yams, like all yams are very starchy and not juicy. Ube are a bit sweeter than other yams, but still not like a fruit would be. And again, ube grow underground; they’re not botanical fruits even. These show that despite their use in desserts, they’re still considered a vegetable.