That is a vintage Tupperware Onion Keeper (specifically, the Tupperware “Onion Saver” bowl, model #1309/1310).
The Perforated Insert: The flat disk with small holes and a center spike sits at the bottom of the bowl. Its main purpose is to elevate a cut onion above its juices and allow air circulation, which keeps the onion crisp and prevents it from turning slimy or molding quickly.
The Spiked Center: The center peg helps hold the onion upright or steady while sealing or moving the container.
The Domed Lid: The translucent lid seals in the strong odor so your refrigerator doesn’t end up smelling like raw onion.
While specifically designed for onions, many people also used it to store halved citrus fruits like lemons and oranges or cut tomatoes.