Preheat your Blackstone griddle with one zone set to medium-high heat for smashing the burger patties and a second zone set to medium-low for toasting the buns and holding finished burgers. Lightly butter the inside of each bun and place them cut-side down on the griddle until golden and crispy, then move them to the warm zone or a plate.

Place each beef ball directly onto the hot griddle. Top with a small handful of the thin-sliced onions. Using a sturdy spatula or burger press—parchment paper can help—smash the onions firmly into the beef, pressing flat to maximize contact with the hot surface. Season each patty with salt and pepper. Let them cook undisturbed for 2–3 minutes until the edges are deeply browned and crispy. Flip each patty so the onions are now on the bottom, caramelizing into the meat. Immediately place a slice of American cheese on each patty. Cover with a melting dome if needed to help the cheese get perfectly gooey.

To build the burger, spread mayonnaise on the bottom bun. Add the cheesy onion smash patty, then top with ketchup, mustard, and pickles. Finish with the toasted top bun.

Seeded Burger Bun: Classic flavor, slight crunch, holds up well—great for traditionalists.

Everything Bagel Bun: Bold, savory, and chewy—ideal for those who love adventurous flavor.

Martin’s Potato Roll: Buttery, slightly sweet, and soft—perfect for smashburger purists.