Is there any sandwich so universally beloved as the burger? Even if experts can't agree on who invented the burger, everyone can pretty much agree that it's the unofficial sandwich of America.

Of course, ask 100 people how to make the perfect burger, and you're likely to get 100 different answers. For a dish that's really pretty basic—grilled meat and a bun—the burger leaves a lot of room for delicious variation. Do you like your patties thick or thin? Just ketchup and mustard or an entire fridge's worth of toppings? And do tomato slices have any right to be there at all?

To determine how to make the perfect burger once and for all, we turned to the most official expert we could find (next to Mayor McCheese, that is): Brad Garoon, the burger-loving blogger of Burger Weekly, and author of the e-book Burger City, documenting the best burger joints in New York City. Below, he outlined six essential hallmarks that the best burgers have in common.

Ground Meat, Cooked Medium Rare

"Half the time you order medium rare and get medium, so you're hedging your bets," Garoon said. Medium rare is the best because "you still get that great char flavor, and the inside is soft and supple. It keeps the juices flowing, and the burger never dries out."

Whereas well done should be avoided because "when the burger is dry, toppings don't melt on it, and halfway through, you get bored."

Ground beef may be the standard, but game meat, turkey, and even veggie patties are fine, as long as they're ground and put between a bun. "But when you get a steak or a fillet of fish, you've moved on to a sandwich," Garoon said.

Potato Roll

"The biggest mistake is a kaiser roll; it's pretty dry," Garoon said. Instead, sandwich the patty between a potato roll, specifically a Martin's potato roll. If that's not available, a sweet brioche bun is a good alternative.

Cheese

And any kind of cheese is good—"as traditional as american or loud as roquefort," he said.

Bacon and Egg

"Bacon in any form is a welcome sight," Garoon said. "It's not a new trend, but a great trend: putting egg on it. It's almost always a great choice."

No Ketchup!

We raised our eyebrows at this one, but Garoon insisted. "Ketchup has no place on a burger, much like it has no place on a steak. You're doing disservice to the meat if you put something as sweet as ketchup on a burger, unless it's terribly dry."

Another no-no? Tomatoes. Why? Simple: they're too slippery and cause the other toppings to fall off. Lettuce and onion, on the other hand, are totally acceptable.

Where to Find the Best Burgers Near You:

So which restaurants truly understand the rules for the best burger recipe? Garoon's website names quite a few, but we have a few additions outside of New York City.

Black Iron Burger | New York, NY
Stop by this rustic eatery for Garoon's favorite burger, The Masterpiece, topped with swiss, caramelized onions, a fried egg, and applewood-smoked bacon.

Kuma's Corner | Chicago, IL
All of Kuma's superlative burgers are named after heavy-metal acts, such as the Lair of the Minotaur, topped with caramelized onions, pancetta, brie, bourbon-soaked pears.

Epic Roasthouse | San Francisco, CA
Sometimes—even when you're at a storied steak house—you just want a burger. Fortunately, you can chow down on Epic's freshly ground half-pound burger made of wagyu beef while enjoying a view of the Bay Bridge.

Little's Food Store | Atlanta, GA
Small patty—check. Grilled onions—check. Potato-roll bun—check. The recipe for a perfect slider.

Casper's and Runyon's Nook | Saint Paul, MN
Made with its signature butcher-cut Black Angus ground chuck, the Nook's version of the classic hometown Jucy Lucy burger stuffs the patty with bacon and pepperjack

Off-Site Kitchen | Dallas, TX
There's no such thing as a plain burger at Off-Site Kitchen. Take the praised Do It Murph-Style, which is topped with roasted-jalapeño and smoked-bacon relish, american cheese, and secret sauce.

Dick's Drive-In | Seattle, WA
Even in its 60th year of business, Dick's Drive-In is doing things the old-fashioned way, serving all-natural beef patties, hand-cut fries, hand-dipped milkshakes, and root-beer floats.

Comet Cafe | Milwaukee, WI
For a state known for its love of all things cow, it's surprising to find one of the country's best veggie burgers here. The walnut-apple burger is just as savory as its meat-made cousins because the veggies are herb-encrusted.

This article was originally written by Liz Juranek, was published in a slightly different format, and has since been modified by our editors.