I made cake tonight for my sons bday party tomorrow. I iced it with buttercream made from the meringue powder. Can I leave the cake out covered overnight or do I need to refrigderate. I also used 2parts shorting and 1 part butter for the icing.. TIA

It will be just fine. The meringue powder nor butter has nothing to do w/needing to be frig'd or not The sugar keeps it from spoiling.