Cake doughnuts, lacking that honeycomb structure of
big yeast bubbles, are often (but not always) smaller, with a puckered little hole.
Let sit until
the yeast bubbles, about 5 minutes.
Set aside for 5 minutes or until
the yeast bubbles.
(If you've ever baked bread, you know you give the yeast a spoonful of sugar to help
the yeast bubble up at first.)
The yeast bubbled, but then the dough hardly rose, (if at all).