Ensure your sourdough starter is active. Feed it 4-6 hours before starting.

In a large mixing bowl, combine the flour, sugar, cinnamon, and salt. Whisk well to distribute evenly.

Pour in the warm water and active sourdough starter. If using melted butter, add it now.

Mix the dough with your hands or a spatula until it comes together. Turn it onto a floured surface and knead for about 5-7 minutes until smooth and elastic.

Place the dough in a greased bowl, cover, and let it rise in a warm place for 1-2 hours or until doubled in size.

Punch down the dough to release the air. Shape it into a loaf by rolling it flat, sprinkling with additional cinnamon sugar if desired, and rolling it tightly.

Place the shaped loaf in a greased loaf pan, cover again, and let it rise for another 30-60 minutes.

Preheat your oven to 375°F (190°C).

Once risen, bake the loaf for 25-30 minutes, or until golden brown and sounds hollow when tapped.

Remove from the oven, cool in the pan for 10 minutes, then transfer to a wire rack for further cooling before slicing.