Tenderize: Use a meat tenderizer to soften the beef slices. This helps break down the fibers, making the meat more tender.
Season the beef slices with Italian seasoning, crushed garlic, and salt. Make sure the seasoning is evenly distributed on both sides of the meat.
Sprinkle the cornstarch (or flour) over the beef slices, rubbing it in to ensure both sides are well-coated.
Sear the beef: Heat the olive oil in a large pot or Dutch oven over high heat. Sear the beef slices for about 2-3 minutes on each side, or until they develop a golden-brown crust. Remove the meat from the pot and set it aside.
Onion: In the same pot, add the sliced onions and sauté them over medium heat for about 3-4 minutes, or until they become translucent and slightly caramelized.
Tomatoes: Add the diced tomatoes to the pot and cook for another 2-3 minutes, allowing them to soften and release their juices.
Simmer: Pour in the marinara sauce and beef broth, stirring to combine. Add the Worcestershire sauce and bring the mixture to a gentle simmer.
Combine: Return the seared beef slices to the pot, submerging them in the stew base. Reduce the heat to low, cover the pot, and let it simmer for 1.5 to 2 hours, or until the meat is tender and the flavors have melded together. Stir occasionally to prevent sticking.
Finish: Once the meat is tender and the stew has thickened, stir in the freshly chopped parsley. Serve the Swiss steak hot, garnished with fresh cilantro.