Combine mayonnaise and seasoning. Can be made ahead and refrigerated.
Split loaf of bread in half horizontally. Spread bottom half with flavored mayonnaise. Layer on turkey, ham, salami, cheese, tomatoes and onion. Spread olive tapenade on top half of bread and place on top of sandwich.
Cut into wedges to serve immediately OR wrap tightly in plastic wrap and refrigerate until ready to serve. OR wrap in aluminum foil and place in preheated 350°F oven and bake for 20 to 25 minutes or until heated through.