Lay the bread slices on a clean work surface. Spread the tomato sauce evenly over the center of one slice. Sprinkle the shredded cheese on top, then arrange the pepperoni slices over the cheese. Place the second bread slice on top to form a sandwich.

Using a sandwich crimper or the rim of a sturdy glass, press down firmly in the center of the sandwich to cut through the bread and seal the edges. Lift away the crusts and discard or reserve for another use.

For a toasted version, heat a lightly oiled non-stick skillet over medium heat. Place the uncrustable in the pan and cook for 2 to 3 minutes per side, until golden brown and the cheese is melted. Transfer to a plate and let cool to room temperature.

Pack the cooled uncrustable into a lunch container, keeping it separate from the carrot sticks and apple slices. Seal the container and include an ice pack in the lunch bag to keep everything fresh.