Combine all the ingredients together in a large bowl, minus the flour. Whisk until well combined.
Using the spatula, fold in the flour one half at a time. Cover with plastic wrap and let dough sit overnight at room temperature.
Place dough on a well-floured surface.
Roll out the dough into a rectangular shape. Spread melted butter over it, followed by a generous sprinkling of sugar. Roll the dough into a log and seal the end by pinching it with your fingertips.
Cut the dough into even-sized pieces with a sharp knife (about 15 pieces). Grease a deep baking dish with butter.
Place the buns into the baking dish. They will have plenty of space between, but will rise and spread during the baking process (see photo).
Preheat oven to 350°F and bake for 35-40 minutes, or until golden brown.