Step 1Combine 1 cup warm water (about 110 degrees), the sugar and yeast in a small, non-reactive bowl and set aside until foamy, about 10 minutes. In a large bowl, combine the flour and 1 1/2 teaspoons salt. Stir in 3 tablespoons oil and the yeast mixture until a sticky dough forms. Turn the dough out onto a lightly floured surface and knead until smooth and elastic, about 5 minutes. Grease a large, clean bowl with 1 teaspoon oil, place the dough inside and cover with a towel. Set aside in a warm spot until doubled in size, about 1 hour.
Step 2Sprinkle cornmeal over the bottom of a 15-by-10-inch baking sheet. Stretch the dough into a large rectangle and arrange on the baking sheet, pulling and stretching to ensure dough entirely covers bottom of sheet. Cover loosely with plastic wrap; set aside and let rise for 45 minutes.
Step 3Meanwhile, heat 2 tablespoons of the oil in a large skillet over medium-high heat. Add the onions, one-quarter teaspoon salt and one-eighth teaspoon pepper and cook, stirring occasionally, until the onions are a deep golden brown, about 15 minutes. Add one-third cup wine and cook, stirring to remove any bits of flavoring from the bottom of the pan, until the wine is absorbed, about 1 minute. Remove from heat and set aside.
Step 4In a small pot, combine the apricots, remaining 1 cup wine, vinegar, honey and one-fourth teaspoon salt. Bring to a boil over high heat, stirring frequently. Reduce the heat to medium-low, cover and simmer until the apricots are very tender, about 20 minutes. Remove from heat and drain, discarding the liquid. Set aside.
Step 5Preheat oven to 450 degrees. In a small bowl, combine the ricotta, 5-spice powder and three-fourths teaspoon salt and set aside.
Step 6Scatter the onions over the risen dough and bake until edges are golden, about 10 minutes. Spoon the ricotta onto the dough and spread out roughly with the back of a spoon. In a large bowl, toss together the radicchio, apricots, remaining 2 teaspoons oil, one-half teaspoon salt and one-eighth teaspoon pepper, or to taste, then arrange on top of ricotta. Bake until dough is cooked through and radicchio is wilted and crispy in parts, about 10 minutes more. Remove pan, cool on a rack. (Recipe can be prepared to this point up to 1 day in advance and kept tightly covered in refrigerator.)
Step 7Bring to room temperature. Just before serving, toss the herbs with the lemon juice, one-eighth teaspoon salt and a pinch of pepper, or to taste, and scatter the herbs over the top. Cut into squares and serve.