The problem was that he was not eating the entire 5.5oz can of food.
To refrigerate half the can did not work, he would not eat it once it
was refrigerated.  I would open a can, put half in a bowl and
refrigerate the other half to be served later, and that did not work.

I tried the lid thing, purchased a lid for the cans.  This worked
sometimes.  Many days I was tossing about half a can of food into the
garbage.  I would put out half the can, he would eat that in a few
hours, then I'd put out the rest and he might or might not eat that.

So I've gone back to something I had tried earlier, and this is once
again working.  I open a new can, put half in a bowl and immediately
put the other half in some saran wrap and put it in the freezer.  And
the next day I just unwrap this frozen pile of food, put it in a bowl
immediately and set it down for him.  He will ignore it initially,
keep coming back to it, and eventually it thaws to where he consumes
it all.  I do break it into chunks when I lay it in the saran wrap, I
figure it helps it freeze faster than putting it in as a solid glob.

But freezing half the can works well for this cat.  I'm not throwing
food in the garbage and the food sits in the bowl less time this way.