In a mixing bowl, combine the bread flour and salt. In a separate bowl, mix the water and sourdough starter until well combined. Gradually add the wet ingredients to the dry ingredients and mix until a shaggy dough forms.

Knead the dough on a floured surface for about 10 minutes until smooth and elastic. Place the dough in a lightly greased bowl, cover, and let it rise at room temperature for about 4 hours or until doubled in size.

In a small bowl, mix together the brown sugar, ground cinnamon, and softened butter until well combined.

Drain the soaked raisins and set aside.

Once the dough has risen, turn it out onto a floured surface and gently deflate it. Roll the dough into a rectangle about 1/2 inch thick.

Spread the cinnamon filling evenly over the dough, leaving a small border around the edges. Sprinkle the soaked raisins on top of the filling.

Starting from one long edge, roll the dough tightly into a log. Pinch the seams to seal and place the log seam-side down in a greased loaf pan.

Cover the loaf pan and let the dough rise for another 1-2 hours, or until it has puffed up.

Preheat the oven to 375°F (190°C). Once the dough has risen, bake it in the preheated oven for 35-40 minutes, or until golden brown and the internal temperature reaches 190°F (88°C).

Remove the bread from the oven and let it cool in the pan for 10 minutes before transferring it to a wire rack to cool completely.