The riddle
What Do You Call a Potato Who Reads the News?
Common tater
Break the answer after its second syllable and a vegetable turns up. Wiktionary gives commentator as /ˈkɑmənˌteɪtəɹ/ and tater as /ˈteɪtɚ/, so the back end of the word is tater, the casual name for a potato. Say the whole answer and then say "common tater": the sounds are the same, with the stress landing a little differently. The pun is about as close as an English pun gets.
Reading against commenting
Wiktionary defines a commentator as a person who comments, especially someone paid to give opinions in the media about current affairs. That is a little different from reading the news aloud, which is what a newsreader does. The riddle ignores the gap. It only needs a job connected to the news that ends in the sounds of a potato.
The same pun in 1903
A 1903 book by Dean Rivers prints the same wordplay as the answer to a different question, "Because he was a common 'tatur (commentator)." Rivers spells the potato half of the pun 'tatur. The pun itself is over a century old, while the question about reading the news is a newer way to ask it.
A vegetable with a long past
Wikipedia says potatoes were first domesticated in southern Peru and northwestern Bolivia about 7,000 to 10,000 years ago. In 2024 China led world production with 94.8 million tonnes, about 24 percent of the total. Another riddle whose answer blends two familiar words: what do you call a fake noodle.