Place the frozen bread dough on a plate or in a lightly greased 8x4-inch loaf pan. Cover loosely with plastic wrap and let it thaw until soft, pliable, and almost room temperature. Do not let the dough rise. Thawing in the refrigerator overnight works well, or you can leave it at room temperature for 2 to 3 hours.

In a small bowl, combine the granulated sugar and ground cinnamon. Stir until evenly mixed.

Make 5 deep slits across the top of the dough, being careful not to cut completely through the loaf. Use a sharp serrated knife and cut about three-quarters of the way down. These slits create the signature pull-apart sections.

Place the dough on a large dinner plate to catch any drips. Brush the melted butter generously over all sides of the dough, between each slit, and on the bottom. Do not skimp here; the butter helps the cinnamon sugar stick and creates that rich flavor.

Generously coat all sides of the dough with the cinnamon sugar mixture, getting plenty into each cut. Use your hands to press the mixture into the slits so every crevice is filled.

Transfer the coated dough to a lightly greased 8x4-inch loaf pan. Sprinkle any remaining cinnamon sugar over the top and drizzle with any remaining melted butter.

Cover loosely with plastic wrap and let the dough rise for 30 to 40 minutes, or until it has risen just above the top of the loaf pan. Do not let it over-rise, or the bread may collapse.

Preheat your oven to 325°F. The lower temperature is important because it allows the inside to bake through without burning the sugary crust.

Bake for 35 minutes, until the bread is golden brown and baked through. If the top starts to brown too quickly, tent it loosely with aluminum foil.

Let the bread cool in the pan for 10 to 15 minutes. Run a knife around the edges to loosen any caramelized sugar, then transfer the bread to a cooling rack.

If desired, drizzle with powdered sugar icing while the bread is still warm. To make the icing, whisk the powdered sugar, softened butter, and 1 1/2 tablespoons of milk until smooth. Add additional milk a few drops at a time until the icing reaches a drizzleable consistency.