Cut 4 large, equal pieces of focaccia bread from the loaf, and cut each open lengthwise. Spread the cut sides of the bread with the red pepper dressing.
Lay the arugula on the bottom slices of bread and top with the roast beef. Arrange the onions and cheese on top, and cover with the top slices of bread. Press closed and wrap tightly in plastic wrap or waxed paper until ready to serve.
Yield: 4 sandwiches