Generously grease one 12-cup muffin tin with softened butter. Set aside. In medium bowl, combine sugar, cinnamon, and salt, and mix until well blended. Set aside.
Turn yeast dough out onto a lightly floured work surface and roll into an 18-by-10-inch rectangle. Brush dough with 2 tablespoons unsalted butter and liberally sprinkle with one-third of the cinnamon-sugar mixture.
Beginning with the long side facing you, tightly roll dough away from you into a log; pinch edge of dough to seal. Cut dough crosswise into 1 1/2-inch pieces. Place each cross-sectional piece into prepared muffin cup and lightly cover with plastic wrap. Place muffin tins in warm place until buns double in size, about 45 to 60 minutes.
Preheat oven to 350 degrees.
Once dough has doubled in size, remove plastic wrap and place on middle rack in oven. Bake until golden and puffed, about 22 to 24 minutes.
Remove from oven and cool slightly on wire rack. In the meantime, melt the remaining 6 tablespoons butter in a small saucepan over medium-low heat. Remove buns from muffin tins. Brush liberally with melted butter and gently roll in remaining cinnamon-sugar mixture. Serve warm.