In a stand mixer, combine all the ingredients for the dough and knead for 5-8 minutes using the dough hook.
Transfer the dough to a bowl, cover it, and let it rise at room temperature for 8-10 hours or in the fridge overnight, If storing in the fridge, remove 2 hours before rolling the dough
On a well-floured surface, roll out the risen dough into a 14x9 inch rectangle.
Spread softened butter over the dough, leaving a ¼ inch margin at the far end.
Mix together brown sugar and cinnamon in a bowl and sprinkle over the buttered dough.
Roll up the dough tightly, starting from the 9-inch side, and place seam-side down, seal the edges.
Cut the roll into 1 inch slices using a floss or sharp knife.
Place the cinnamon buns in a greased 9x13 inch baking pan lined with parchment paper for extra protection.
Cover the pan with a towel and let the buns rise for another 30-45 minutes.
Preheat oven to 350°F and bake for 20-25 minutes or until slightly golden brown at the edges.
Allow to cool for 5-10 minutes before frosting. Enjoy your delicious sourdough cinnamon buns!