In a mixer bowl, combine the flour, sugar, zest, yeast, and salt.
4 cups (500 grams) unbleached bread flour, 2 tablespoons granulated sugar, 1½ teaspoons instant yeast, 1 teaspoon orange zest, 1 teaspoon salt
Measure out the water in a large (2 cup is ideal) measuring cup. Add the eggs and oil, and whisk lightly.
¾ cup (177 grams) lukewarm water, 2 whole eggs, 2 egg yolks, 2 tablespoons canola, safflower, or other neutral oil
Add the wet ingredients to the mixing bowl, and mix on low speed using the paddle attachment until combined.
Switch to the hook attachment and mix on medium speed for 8 minutes, adding small amounts of water or flour as necessary to get the dough to clear the sides of the bowl. The final dough should be soft and not sticky at all.
Form the dough into a round, lightly oil a bowl (I use the same mixing bowl), cover with plastic wrap, and let rise in a warm, draft-free place until about doubled, 1 to 2 hours (Rise #1 of 3).
Degas, re-form into a round, and again let rise until about doubled, 1 to 2 hours (Rise #2 of 3)
Shape the dough (see text for some suggestions) and let rise until doubled again (Rise #3 of 3).
At least 30 minutes prior to baking, preheat the oven to 325°F.
Right before baking, brush the loaf with the reserved egg whites (keep for one more brushing). Top with poppy seeds or sesame seeds, if using.
poppy seeds or sesame seeds for topping
Bake on a middle shelf for 20 minutes. Brush one more time with reserved egg wash to ensure coverage of the entire loaf.
Continue baking until internal temperature is 190 to 195°F, the crust is a rich caramel brown, and the bottom sounds hollow when thumped. This should take about 40 to 60 minutes in total, depending on the size of your buns.
Cool for at least one hour.