This formation, called "the eye of the Sahara", has mystified geologists for decades

Nope
There’s no evidence of an impact, there’s no shock metamorphism that would result from a hypervelocity impact

The best working theory right now comes from a couple of Canadians. Basically its a dome in the crust that has been eroded. https://www.businessinsider.com/the-eye-of-the-sahara-is-still-a-mystery-2016-7