1 loaf (8 to 10 ounces) focaccia bread, cut horizontally in half
4 ounces smoked mozzarella or provolone cheese, sliced 1/8 to 1/4 inch thick
1 medium plum tomato, cut into 1/4-inch thick slices
Cut beef steak lengthwise in half, then crosswise into 1/8 to 1/4-inch thick strips. Combine 2 tablespoons pesto and beef in medium bowl. Cover and marinate in refrigerator 30 minutes to 2 hours.
Heat oven to 350°F. Remove some bread from center of cut sides of loaf if very thick, creating a pocket. Spread remaining 2 tablespoons pesto evenly over cut sides of bread; top each half evenly with cheese. Place on metal baking sheet. Bake in 350°F oven 8 to 10 minutes or until heated through and cheese melts.
Meanwhile heat large nonstick skillet over medium-high heat until hot. Add 1/2 of beef; stir-fry 1 to 3 minutes or until outside surface of beef is no longer pink. (Do not overcook.) Remove from skillet. Repeat with remaining beef.
Using slotted spoon, place beef over bottom half of bread; top with tomatoes. Close sandwich, pressing together slightly. Cut into 4 wedges.