Dissolve the yeast in 1/2 cup warm water (roughly 105-115F)for about 1 minute. Stir the yeast and water around, then add orange zest, orange juice, sugar, salt, egg, butter, and 1 1/2 cups of flour. Using a mixer, beat everything together on low, scraping down the sides as needed. With a wooden spoon, stir in enough of the remaining flour to make a dough easy to handle - about 1 1/2 - 2 more cups. You are looking for a dough that is not sticky and will spring back when poked with a finger.