In boiling, salted water, cook the linguine until al dente; reserve 1-1/2 cups pasta cooking water. In a large,deep skillet, cook the bacon over medium heat until crisp. Discard all but 3 tablespoons bacon fat, then add the onions to the skillet and cook over medium-high heat, stirring, until softened. Add the pasta cooking water and bring to a boil. Stir in the linguine and remove from the heat. Stir in the egg yolks, one at a time. Add the bacon, season with pepper and sprinkle with parmesan.