Updated: Aug 5, 2020
"Throw out your onions and check your freshly pre-made foods for onions possibly from the contaminated source" which is stated by the CDC to be supplier Thomson International. Other names include TLC, Tender Loving Care, Majestic, Thomson Premium/International, El Competitor, Hartley's Best, Imperial Fresh, Onions 52, Kroger, Food Lion, & Utah Onions.
Per the CDC Guidelines "Do not eat, serve, or sell any onions on the recall list."
Illnesses seem to be coming from the source of raw onions. See a 2014 study done on the Survival or Growth of Inoculated E. coli 0157:H7 and Salmonella on Yellow Onions under Conditions Simulating Food Service and Consumer Handling and Storage . The results in the study show that storing the onions at 4⁰C (typical refrigerator temperature) can prevent the microbe from growing, however, it does not kill off the microbe. A preliminary study where the onion was pealed down to the 3rd layer or beyond showed significant decrease and even non-detect levels in contamination.