All ingredients ready? Let's begin!
Sprinkle 1/2 teaspoon of salt over all sides of each steak. Set the beef aside to come to room temperature.
In a large skillet over medium-high heat, warm the olive oil. Sear each steak for 2 minutes per side. Remove the steaks to a platter.
Add the onion slices and garlic to the skillet. Sauté until the onions and garlic become fragrant, approximately 1 minute.
Add the bell peppers and cook, stirring occasionally, until the vegetables have softened, approximately 4 minutes.
Stir in the tomatoes, pepperoncini, oregano, cayenne, and water. Bring the sauce to a simmering boil.
Place the steaks in the sauce, reduce the heat to a low simmer, and cook for about 6 minutes, turning the steak over halfway, until the meat is cooked to medium-rare.
The internal temperature of the steaks should be 125°F for medium-rare and 135°F for medium.
Remove the steaks to a clean cutting board and allow them to rest while the sauce reduces. Simmer the sauce for 3 to 5 minutes until the consistency you like is achieved.
Combine the cheeses in a bowl while the sauce is simmering.
Slice the steaks thinly across the grain.
Place the steaks on oven-proof plates. Spoon the sauce over the steak portions. Optional: Top with equal portions of the cheese and place under a broiler for less than a minute just until the cheese melts. Alternatively, serve the cheese on the side.
Top the steaks with parsley.
Serve immediately while warm with individual bowls of spaghetti that have been seasoned with salt and pepper and drizzled with olive oil on the side.