I have a question about the recipe "Onion Tarte Tatin" from Erin McDowell. Should I do an egg wash on the pastry?
You could if you want, but I don't see the point.
After all, this is a tarte tatin and as such, it is inverted before serving. Thus, if you egg wash the pastry for shininess, no one is going to see it because it will be facing the serving plate/tray.
But do what you want.
Best of luck.