If I am baking cake (from box mix or from scratch) and I don't have any fresh eggs, what must I take into account if I want to use powdered eggs or pasteurized liquid eggs instead? Will this work, and under what conditions?
Pasteurized liquid eggs should work 1:1 as a substitute for whole eggs. Obviously, at this point, you cannot separate the yolks and whites, so you cannot use them for recipes which require separation. You would use approximately 1/4 cup of pasteurized egg per large egg in the original recipe.
Similarly, you can use reconstituted powdered egg, although the flavor may not be the same. I wouldn't do this in a yellow cake whose flavor is dependent on eggs, but in a chocolate cookie, it might be perfectly acceptable. Again, reconstitute the powder first according to its directions, so it is liquid, and then use about 1/4 cup per large egg from the original recipe.