Apples might be the forbidden fruit in ancient literature, but for Martha Stewart, they're the not-so-fancy fruit that turns a tuna salad sandwich into something phenomenal.

Stewart’s preference to cut up quarter-inch apple slices and add them to her tuna salad recipe amps up the crunch and texture factors in the sandwich.

The sweetness of the fruit enhances the savory in the tuna by bringing in the fish's culinary opposite from a flavor standpoint, helping to balance all the flavors.

The sugar in the apples may even go as far as "turning on" the savory flavor, effectively making the tuna even umami-er, so to speak.

Stewart's sandwich recipe also boasts a variety of sour or salty flavors, like lemon, celery, and the sourdough bread she champions for use in this dish.