McDonald’s announced changes to some of its most popular menu items last week, affecting the Big Mac and McDouble, among other things.

The fast food giant claims the changes will improve the flavor of its top-performing burgers.

The improvements come down to four main changes, according to McDonald’s: better, softer buns, consistently melted cheese, a better sear on the patties and, simplest of all, more Big Mac sauce.

The chain says it has also started adding white onions to the patties as they are searing to improve the flavor.

“I’ll always remember my first burger from McDonald’s. And now my culinary team and I have the best job in the world: thinking about ways to bring even more of that iconic McDonald’s taste to fans,” McDonald’s USA senior director of culinary innovation Chad Schafer said in a statement.

“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,” he added.

McDonald’s is starting to introduce the burger changes in Los Angeles, Seattle, Portland, San Francisco, Sacramento, Phoenix, Las Vegas, Salt Lake City, Denver, Boise and Tucson.

It says many stores in the surrounding area will also participate.

US markets are not the first to taste the improved versions of McDonald’s classics.

The chain tested the changes in Australia, Canada and Belgium last year.

McDonald’s hopes to roll out the burger improvements to all stores by 2024.