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.
Step 4: Bake the cupcake recipe and cool. Bake the cupcakes at the same temperature called for in the cake recipe, but reduce the baking time by one-third to one-half (cupcakes usually bake for 15-20 minutes). Check doneness by inserting a wooden toothpick into the center of the cupcake.