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.
6 Scoop into cupcake papers about 1/2 to 3/4 full and bake for 19-21 minutes at 350F, being sure to rotate the pan after the first 15 minutes of baking. Afterwards allow to cool for 5 minutes before taking the cupcakes out of the cupcake tin and allowing them to fully cool on a wire rack. Frost cooled cupcakes.