The author of this recipe shares that any grilled sandwich starts with good bread. Same is true for this one. That’s why she used a rustic sourdough boule that’s made with whole wheat and rye flour. The bread is sliced thickly and layered with tomatoes, mozzarella cheese and arugula pesto. The arugula pesto has a little bit of a lemony flavor. The sandwich is then lightly grilled in a skillet and heated in the oven for that golden crisp perfection.