From my favorite recipe site:
1 T butter
4 slices bread
1 T cinnamon
1 large apple, cored and thinly sliced
1. Set oven to broil.
2. Spread butter on one side of each slice of bread. Place apple slices on buttered side of bread. Sprinkle cinnamon on top. Place bread on a baking sheet.
3. Place in a preheated oven until toasted, about 2 minutes.