Make the dough: Dilute 1 teaspoon of sugar into the warm milk (about 110°F/43°C). Sprinkle the yeast and let sit for 5 – 10 minutes until it is bubbly. If it is not bubbly, the yeast is no longer active and unfortunately cannot be used.

In a bowl, combine flour, sugar, and salt. Pour the yeast mixture in. Add the egg and mix well.

Add the melted butter. Mix until it is fully absorbed. Transfer onto a lightly floured surface.

Knead the dough for 10 – 15 minutes. Round it into a ball once it turns smooth, elastic, and not tacky.

Make the filling/topping: Stir together the cinnamon and sugar in a bowl. Set aside.

Shape the dough: Transfer dough onto a work surface. Roll into a ¼-inch (0.6 cm) thick rectangle. Brush with melted butter throughout the surface. Then sprinkle enough cinnamon sugar filling evenly. Keep the leftover mixture as a topping later.

From the long edge, roll the dough until the end to form a log. With a serrated bread knife, slice the log into 12 equal-sized pieces.

Bake in a preheated oven at 350°F (180°C) for 20 - 25 minutes or until golden brown. Let cool on a cooling rack.

Remove the sugar bun from the pan. Brush each top and side with melted butter, then sprinkle the cinnamon-sugar mixture to coat it evenly.