In a large baking dish, whisk eggs, milk and cinnamon, set aside. Make 2 sandwiches with the bread and apple pie filling. Place sandwiches into egg mixture. Let soak until egg mixture is completely absorbed into the bread, turning sandwiches once. Takes about 3 minutes.
On a griddle over medium-high heat, melt 1 tablespoon butter. Cook sandwiches on the griddle until brown and heated through, about 4 minutes per side. Cut each sandwich in half. Transfer to plates and serve with additional butter. Top with powdered sugar if desired.