Roast Beef Sliders

I love to cook big Sunday dinners for my family when time allows, and almost better than the dinner is finding new and tasty ways to re-purpose the leftovers. This recipe is a great way to use up leftover roast beef. For an even more savory flavor (if that's possible!), use a smoked variety of cheese. —Shannon Dobos, Calgary, Alberta Total TimePrep: 20 min. Bake: 25 min. Makes 1 dozen Ingredients 1 medium onion, thinly sliced1 tablespoon olive oil3 tablespoons mayonnaise2 tablespoons