Place a large skillet over medium-high heat with 2 turns of the pan of EVOO, about 2 tablespoons. Season the steaks with salt and pepper, and sear in the pan (working in batches if need be) until the steaks have a nice crust on the outside, about 3 minutes per side.
Remove the cooked steaks from the skillet and reserve warm on a plate. Return the skillet to medium-high heat and add the pancetta or bacon, if using. Cook until golden brown and crispy, about 5 minutes.
Add the onion and garlic to the pan, and cook until tender, about 5 minutes. Add the balsamic vinegar, brown sugar, Worcestershire and tomato sauce to the pan, season with salt and pepper, and bring up to a bubble. Reduce the heat to medium and simmer the sauce until lightly thickened, 3-4 minutes.