The other reason to visit Sid's is to eat the fried onion burger, which happens to be one of the best of a local breed that was invented in El Reno (at a spot, now gone, called Hamburger Inn) during the Great Depression. The burger's distinguishing feature—lots and lots of onions cooked right into the patty—began as a way of stretching a day's ground-beef supply. Marty, who started making the local specialty as a grill cook 41 years ago, places a small ball of ground beef on a hot flattop griddle, showers the meat with a heap of thinly sliced vidalia onions, and then presses the patty down until the onions and beef become one. When the burger becomes crunchy and browned on the bottom, it's flipped so that the same thing can happen to the other side. The result is a burger like none other, one that sparkles with sweet, caramelized-onion flavor.