In the a bowl of a stand mixer fitted with a dough hook, combine the flour, cinnamon, orange zest, cinnamon, yeast, salt, orange blossom water, eggs, and leaven.
Mix on low speed until all of the ingredients are incorporated.
Turn the mixer speed to medium-low and continue mixing until the dough developed 50 % of gluten.
Then, add the sugar in 5 or 6 batches while mixer is running. After each addition, mix for a minute or two before adding the next one.
Continue to mix until the dough reaches full gluten development. The dough should be pulling away from the bowl.
Add the softened butter all at once. Mix on low-medium speed until it is fully incorporated and the dough has returned to full gluten development.
Transfer the dough to a lightly buttered container.
Cover and ferment at room temperature until the dough is nearly doubled in bulk. It took about 3 hours in my case. It varies according to your room temperatures.
Cover with a plastic wrap and refrigerate overnight.