Preparation Preheat oven to 375°F. Sauté bacon in heavy large skillet over medium-high heat until slightly crisp. Drain all but 1 tablespoon bacon drippings from skillet. Add onions to bacon and sauté over medium heat until onions are very tender but not brown, about 20 minutes. Cool. Whisk egg, sour cream, salt, pepper, and nutmeg in large bowl to blend. Stir in cooled onion mixture. Roll pizza dough out on lightly floured surface to 13x10-inch rectangle. Transfer to baking sheet. Spread onion mixture over dough, leaving 1/2-inch plain border around edges. Sprinkle with caraway seeds. Bake tart until onion custard is set and crust is golden brown around edges and brown on bottom, about 25 minutes.
Preparation Preheat oven to 375°F. Sauté bacon in heavy large skillet over medium-high heat until slightly crisp. Drain all but 1 tablespoon bacon drippings from skillet. Add onions to bacon and sauté over medium heat until onions are very tender but not brown, about 20 minutes. Cool. Whisk egg, sour cream, salt, pepper, and nutmeg in large bowl to blend. Stir in cooled onion mixture. Roll pizza dough out on lightly floured surface to 13x10-inch rectangle. Transfer to baking sheet. Spread onion mixture over dough, leaving 1/2-inch plain border around edges. Sprinkle with caraway seeds. Bake tart until onion custard is set and crust is golden brown around edges and brown on bottom, about 25 minutes.