I used to make a grilled cheese pizza sandwich when my son was a youngster.

Melt butter in skillet.
Between two slices of bread place your cheese slice, with 4 or 5 slices of pepperoni, spread pizza sauce on top, then add second slice of bread and grill on both sides.

Here's recipe I found:

1 tablespoon butter, softened
2 slices bread
1 slice provolone cheese
6 slices pepperoni
3 tablespoons pizza sauce
Additional pizza sauce, optional
Directions:
Butter one side of each slice of bread. Place one slice in a skillet, butter side down. Top with the cheese, pepperoni, pizza sauce and second bread slice, butter side up. Cook over medium heat until golden brown, turning once. Serve with additional pizza sauce if desired. Yield: 1 serving.