cherry pie vs piece of cake

cherry pie

noun
  • A pie baked with a cherry filling. 

  • Heliotropium arborescens. 

  • Any of various willowherbs 

piece of cake

noun
  • Used other than figuratively or idiomatically: see piece, cake. 

  • A job, task or other activity that is pleasant – or, by extension, easy or simple. 

How often have the words cherry pie and piece of cake occurred in a corpus of books? (source: Google Ngram Viewer )