In a bowl, combine the buttermilk and sugar. Set aside.
With a wooden spoon or a in the stand mixer (using the dough hook), combine the flour, yeast and salt. Add the buttermilk mixture and mix thoroughly until the dough begins to form.
Gradually add the butter and knead for about 5 minutes in the stand mixer or on a floured surface. The dough will be soft and slightly sticky. Place the dough in a clean and lightly oiled bowl. Cover the bowl with a damp cloth and leave in a warm and humid place for about 1 hour.
Generously butter a bundt pan. Set aside.
In a bowl, pour the melted butter. In another bowl, combine the brown sugar, sugar, and cinnamon. Set aside.
Remove the dough from the bowl and cut into approximately 40 pieces of various sizes. Without overworking the dough, shape balls with the palm of your hands.
Dip the balls in the butter to coat. Roll in the brown sugar mixture and place them progressively into the pan. Pour the remaining brown sugar mixture and butter on the dough balls into the pan. Cover with plastic wrap and let rise in a warm and humid place for 45 minutes.
With the rack in the middle position, preheat the oven to 180 °C (350 °F).
Remove the plastic wrap and bake for 40 minutes for a dark bundt pans or for 45 minutes for a pale bundt pan, or until the caramel is golden brown and bubbly around the edges. Immediately unmould on a serving platter. Let cool for 15 minutes before serving. Eat warm or cold, preferably the same day.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.