Roast Beef Sandwiches with Olive Tapenade

This isn’t your typical roast beef sandwich. We skip the usual horseradish, mustard, and cheese in favor of bright California flavors—basil aioli, briny olive tapenade, thick slices of late-season tomatoes—all piled high with thin slices of roast beef. For sliders, divide the fillings among mini ciabatta rolls, then wrap them individually in parchment paper and secure with kitchen string for safe picnic transport.