The poffertje machines would not work as they wouldn't be deep enough for a doughnut. They are like minature pikelets. So when you go to markets and so on, you get a plate of them with butter, icing sugar and select maple syrup, lemon or honey to go on top if you like.
I did see in the recent Target magazine a Dora Cup Cake machine, like the pie maker's only for cup cakes, it definitely looked deep enough for what you need. You could check that out.