Follow the Soft Sourdough Master Dough Recipe to the end of the second rising stage. Punch down dough, dump onto a lightly floured. Roll dough out into a 12"x18" rectangle.
Spread or pour butter over the dough and evenly coat the rectangle. If the butter is melted, sometimes I let it sit a couple minutes on the cool dough to let it thicken up as it cools down.
Mix your cinnamon and sugar together in a bowl.
Sprinkle your cinnamon sugar mix over the butter.
Gently roll your rectangle into an 18" log.
Cut your log into 12-18 cinnamon buns, depending on how big you want them.
Line or grease a half sheet pan (or cookie sheet with sides/a lip to it) and arrange the buns on the tray. Closer together if you want them 'pull apart' or spaced farther if you want them stand alone.
Cover pan and let rise 2-3 hours. If your house is REALLY cold, like below 60F/15C, I like to tuck a cast iron pan in the oven to help it hold heat, turn oven on for a minute or two, then turn oven off. Tuck the covered pan in and let the buns rise in there.
When they are doubled and looking fluffy, (don't forget to take the pan out of the oven if it's in there!) and preheat oven to 375F.
Bake for 15 minutes, flip around then bake another 10 minutes. Take their internal temp with an instant read thermometer - because everyone's ovens cooks different, your buns are probably different sizes than mine...sourdough takes longer to bake than yeast dough...instant read is best way to know they are done and not have doughy buns. You want them to be 190F-200F
When theyre out, this is the fun part! You can eat right away, glaze using the one above, or use your own frosting. If you're frosting them, they need to cool down for about half an hour or your frosting will all melt off.