Vidalia, Walla Walla and Maui's are sweeter then regular white onions . They're well suited for an onion tart. They can be found in the early summer months. Blue cheese adds a flavorful element to the onions but the tart can also be made without the cheese. Source: unknown
In large skillet over medium heat, cook bacon til golden, about 8 minutes. Reduce heat to low and add butter, onions salt and pepper. Cook onions, stirring occasionally, for 45 to 55 minutes or til deep golden brown and jam like. Taste for seasoning. Use now or cover and refrigerate for up to one day.
Put 2 pastry sheets side by side on a lightly floured board. Press edges of sheets together and lightly crimp. To create a circular pastry, cut 2 inches dough form one long end of rectangle and aitch to top, crimping edges together to seal them. Gently roll dough to smooth it out. Place in an 11 inch round tart pan with a removable bottom. Trim off excess-dough. Freeze 20 to 30 minutes. Preheat oven to 425. Fill crust with caramelized onions and optional blue cheese. Bake til crust is golden, about 25 minutes. Let cool slightly and serve warm, or serve at room temperature. Makes 10 to 12 appetizer servings