1. Preheat oven to 425 degrees Fahrenheit (220 degrees Celsius).
2. Prepare cran-apple mixture, if using.
3. Line cupcake trays with 18 paper liners; fill 2/3 full with muffin batter.
4. Drop 1 teaspoon jam or cran-apple mixture into the center of each cup, pressing in slightly.
5. Place pans in oven, bake 15 minutes, and remove to cool.