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.
Tips. 1  Two 8- or 9-inch pans of cake batter typically require 30 to 35 minutes in the oven, so you'll reduce this time by at least 10 minutes for standard-sized muffin pans. 2  Test your muffins or cupcakes to be sure they are done by inserting a toothpick in the center of one.