In a large bowl, dissolve yeast in water.
Add milk, butter, sugar, salt, lemon peel, and eggs; mix to blend well.
Beat in flour, 1 cup at a time, beating well after each addition, to make an elastic dough.
Cover bowl and let dough rise in a warm place until doubled (about 1 hour).
Beat down; spoon about 1/4 of dough into each of 2 well-greased 10-cup plain or fancy tube pans or ring molds, spreading in thin, even layers.
Spoon 1/2 the filling in an even ring over dough in each pan; filling should not touch pan sides or center tube.
Top each with 1/2 the remaining dough, smoothing it over filling and against pan sides.
Cover and let rise until puffy (about 20 minutes).
Bake in a 350° oven for about 45 minutes or until golden brown.
Cool in pans for 5 minutes; then turn out on racks.
Dust with powdered sugar just before serving.