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

Using a sandwich crimper or the rim of a glass, press down firmly in the center of the sandwich to seal the edges and cut off the crusts. Remove the crusts and discard or save for another use.

Optional: Heat a lightly greased non-stick skillet over medium heat. Cook the uncrustable for 1-2 minutes per side, until golden brown and the cheese is melted. Remove from the skillet and let cool to room temperature on a wire rack.

Pack the uncrustable in a lunch container, keeping it separate from the carrot sticks and apple slices. Seal the container and place it in a lunch bag with an ice pack to keep everything fresh until lunchtime.