How a microwave heats food without making the plate equally hot

I understand the basic idea that a microwave makes water molecules move, but I can't reconcile it with what happens in my kitchen. Sometimes a bowl is almost too hot to touch while the food has a cold spot in the middle. Other times the plate stays cool. Is the dish absorbing some of the microwave energy itself, or is it mostly being heated by the food touching it? I'd love an explanation that covers both cases without pretending everything warms evenly.