Special equipment: Six 4-inch unglazed terra-cotta flower pots
Heat 1 tablespoon of the oil in a large skillet over medium-high heat. Add the onions, and cook, stirring frequently, until golden brown, about 8 minutes. Remove the skillet from the heat, and let the onions cool.
Put 1/2 cup warm water (about 110 degrees F) and the sugar in the bowl of an electric stand mixer fitted with a dough hook (or into a large bowl if you'll be kneading by hand), sprinkle the yeast over the water and let sit until foamy, about 5 minutes.
Add 1 1/2 cups warm water (about 110 degrees F), the browned onions, the 2 remaining tablespoons oil, the flour, rosemary and salt, and mix on medium-high speed with the dough hook (or a wooden spoon) until a dough forms. Knead on medium-high speed, adding a little flour if the dough sticks to the bowl, until the dough is smooth and elastic, about 8 minutes (or turn the dough out onto a lightly floured surface and knead, dusting lightly with flour if necessary, until smooth and elastic, about 10 minutes).
Brush a large bowl with olive oil. Add the dough, cover with plastic wrap and let stand at room temperature until more than doubled, 1 to 1 1/2 hours.
Meanwhile, cut out circles of parchment the diameter of the flower pot bottoms, and place 1 circle in the bottom of each pot. Cut long, wide strips of parchment to fully line the sides. Coat the parchment with cooking spray.
Punch the doubled dough down, and evenly divide into 6 pieces. While holding a piece of dough, tuck the edges under to form a ball, then place it seam-side down in a prepared flower pot. Repeat with the remaining dough balls, and let stand, uncovered, at room temperature until more than doubled, 1 to 1 1/2 hours more. (The dough will rise above the flower pot rim.)
Position an oven rack in the center of the oven, and preheat to 375 degrees F. Bake the bread until dark golden brown, 25 to 30 minutes. Remove from the oven, and brush the top of each loaf with melted butter. Let cool until warm or room temperature, and serve. (Or wrap with plastic wrap and store at room temperature for up to 2 days.)
From Food Network Kitchen