That level of caramelization on onions will take about 60 minutes on low heat. I swear these are the best caramelized onions!

Sherry and thyme-infused caramelized onions top a Gruyere burger in this French onion burger made in the air fryer.

"This is the ORIGINAL best burger in town. Grab a beer ... Burger at Father's Office lives up to the hype. Topped with caramelized onions, arugula, gruyere, and blue cheese, it's sure to satisfy ...