Chopped roast turkey and soft red onions make these Hawaiian-roll sliders a warm cheddar sandwich rather than another cranberry-and-Swiss tray. Cook the onions until they lose their sharp bite, then warm the turkey with a little broth before it goes between the rolls. That gives the sweet bread a shorter bake and helps the filling heat evenly across the whole slab. Spread the chopped meat level instead of leaving one tall patch in the center, where the rolls would have to keep baking while the middle catches up. Let the tray rest briefly before cutting so the melted cheddar holds the smaller turkey pieces inside each slider.