Diathermy for food!

From Electronics magazine, Nov 1933.

Note that cooking by HF waves was already familiar in industrial and medical applications. This was the first suggestion of home use for “bun sandwiches”. [Was hamburger trademarked? Apparently not, but cheeseburger was trademarked.]

Restaurants were starting to use HF ovens around 1960. I remember trying an electronic hamburger in a roadside cafe. The oven was fascinating, but the hamburger was too dry and tasted wrong.