As a rule, a CTE will NEVER improve performance. A CTE is essentially a disposable view. There are no additional statistics stored, no indexes, etc. It functions as a shorthand for a subquery. In my opinion they can be EASILY overused (I see a lot of overuse in code in my job).
Check the cupcakes at the minimum baking time. If the recommended baking time is 18-22 minutes, check them at 17 or 18 minutes (just a quick peek, make sure not to let too much heat out of the oven). If the tops are rounded and no long appear wet, they may be done.
Remove the mini cupcake pan from the oven, using potholders, and place on a cooling rack for 10 minutes. Once cool enough to touch, remove the cupcakes from the pan and set on another rack to cool completely before decorating. Step 7. Line the pan with new mini cupcake liners and repeat the steps to bake another batch.