(NEXSTAR) – Your Big Mac taste a little different lately? McDonald’s said it’s been tweaking the way they make their signature burgers in about a dozen large cities, and plans to roll out the changes nationwide.

The changes are subtle, but McDonald’s said Monday they’ve resulted in the company’s “best burgers ever.” It starts with new buns, that McDonald’s said are “softer” and “pillowy” before they are toasted until they’re golden.

Slathered on those buns will be more Big Mac sauce, the proprietary special sauce the company first developed in 1968 (though the recipe has been tweaked a few times over the decades).

McDonald’s is also going to start adding onion to patties while they’re on the grill. The caramelized onions should have a sweeter flavor, rather than the sharp taste of a raw onion.

For those who like a slice of American on their burgers, the recent improvements also mean “perfectly melted cheese,” McDonald’s said.

“We found that small changes, like tweaking our process to get hotter, meltier cheese and adjusting our grill settings for a better sear, added up to a big difference in making our burgers more flavorful than ever,” Chad Schafer, the company’s senior director of culinary innovation, said in a press release.

The changes are being applied to the preparation of the signature Big Mac, the McDouble, and the classic cheeseburgers and hamburgers.

So far, McDonald’s said it has already changed the way burgers are flipped in Boise, Denver, Las Vegas, Los Angeles, Phoenix, Portland, Sacramento, Salt Lake City, San Francisco, Seattle, Tucson, and their surrounding areas.

The fast food chain said it plans to implement the changes across the U.S. by next year.

In addition to rethinking the way it prepares food, McDonald’s is also reportedly restructuring the way it does business. The company temporarily shut some U.S. offices earlier this month and laid off hundreds of employees, the Wall Street Journal reported.