For the sun-dried tomato olio: Combine the sun-dried tomato pesto, mayonnaise, and olive oil in a small bowl. Stir until well blended.
In medium saucepan, fry Margherita(R) Pepperoni over low heat for 1 to 2 minutes on each side, or until edges begin to curl.
Toast or grill sliced focaccia until crispy.
Layer pepperoni and cheese on the bottom slices of focaccia bread, distributing evenly among the 4 sandwiches. For melted cheese, place built sandwich bottoms on baking sheet. Bake at 225 degrees for 3 to 5 minutes or until cheese melts.
Remove sandwich bottoms from heat. Add sun-dried tomato olio, top with baby arugula, close with top half of bread.