For the sauce: Heat a large Dutch oven over medium-high heat. Add the oil. Season the meat evenly with 1/2 teaspoon salt and add to the hot pan. Cook until the meat is deep brown on the first side, about 4 minutes. Flip and continue to cook until deep, dark brown, an additional 3 minutes on each side. Remove the meat to a plate.
Reduce the heat to medium and add the onions and an additional 1/2 teaspoon salt. Stir with a wooden spoon, scraping up all the bits from the bottom and coating the onions in the oil from the pan. Cook the onions, stirring often, until deep golden brown, 25 to 30 minutes.
Add the garlic, carrots and celery and cook until fragrant and soft, another 2 minutes. Clear a little space in the pan so you can see the bottom. Add the tomato paste to that spot and toast the paste, stirring often, until deep red, about 2 minutes. Stir the paste into the vegetables and deglaze with the Marsala. Simmer for 3 minutes to reduce slightly. Place the meat back into the pan and add 3 cups water to cover three-quarters of the way. Nestle the Parmesan rind into the sauce. Reduce the heat to maintain a gentle simmer. Cover with a lid just slightly ajar and simmer, stirring occasionally to prevent sticking, until slightly reduced and the onions are practically melted into the sauce, about 2 1/2 hours.
Season with the remaining 1 teaspoon salt. Remove the piece of meat and the cheese rind. Discard the rind and save the beef for another use. Using a handheld immersion blender, pulse the sauce to even out the consistency. Stir in the butter until combined. Remove 1 1/2 cups of the sauce and reserve for the assembly.
For the meatballs: Preheat the broiler to high.
Mix together the milk, bread and egg with a fork in a medium bowl and let the mixture sit for 5 minutes to thicken. Stir in the Parmesan, oregano and salt. Using your hands, mix in the beef until just combined. With damp hands, scoop 1/2-teaspoon mounds and roll into uniform balls. Place on a rimmed baking sheet. Broil until browned, about 7 minutes. Set aside.
Reduce the oven temperature to 350 degrees F.
For the filling: Heat a small skillet over medium heat. Add the oil and bacon and cook, stirring often, until the bacon is crispy and browned, about 5 minutes. Pour off all but 1 tablespoon of the fat. Stir in the peas and salt and remove from the heat.
For the assembly: Bring a large pot of water to a boil. Season well with salt. Add the pasta and cook for 2 minutes. Using tongs, remove the pasta from the water and add directly to the sauce in the Dutch oven. Sprinkle the bare pasta with 1 1/2 cups Parmesan and toss well with the sauce. Add 1/2 cup pasta water to loosen slightly and help the sauce coat the pasta, if needed.
Using the tongs, place half of the sauced pasta in the bottom of a springform pan. Spread 1/2 cup of the reserved sauce on top of the pasta. Sprinkle with the smoked provolone. Follow with the pea mixture, then the meatballs. Sprinkle the meatballs with 1/2 cup Parmesan. Press down slightly to pack. Top with the remaining pasta and 1 cup reserved sauce. Press gently to compress. Top the pasta with the remaining 1 cup Parmesan.
Place on a rimmed baking sheet and bake until golden brown on top, 50 to 60 minutes. Allow the timbale to rest for 30 minutes before running a knife around the edge and unmolding. Slice with a thin, sharp knife to serve.