For the bacon sauce: Cut the bacon into pieces. Using a big saute pan or skillet that has a cover, cook over medium heat until almost crispy. Don't drain the fat. Add the onions to the pan. When the onions are almost cooked and start to become translucent, add the garlic and salt and pepper to taste. Cook for 1 to 2 minutes, and then add tomatoes and bring to a boil. Reduce the heat, cover and simmer on low for about an hour to an hour and a half.
For the meatballs: Preheat the oven to 425 degrees F. Grease a baking sheet. In a large bowl, combine the beef, breadcrumbs, Parmigiano-Reggiano, parsley, garlic, eggs and some salt and pepper. Form into 1- to 1 1/2-inch meatballs and place on the prepared baking sheet. Bake for 5 minutes. Then turn the oven down to 350 degrees F and bake for an additional 10 minutes. Make sure to turn every few minutes to brown on all sides.
Cook the bucatini according to the package directions.
Serve the bacon sauce over the pasta with the meatballs on the side. Garnish with freshly grated Parmigiano-Reggiano.