Heat a cast-iron skillet over high heat until very hot. Add enough oil to coat the pan. Season the steak with salt. Place the steak in the hot pan and cook until browned, about 4 minutes per side. Remove from the heat and allow to rest 5 minutes before slicing on the bias.
To the same skillet, add the bacon and cook over medium heat until the fat begins to render and the bacon starts turning golden brown, about 3 minutes. Add the onions and cook until tender, about 4 minutes. Then add the mushrooms and tomatoes and cook until everything is combined and almost cooked through, about 5 minutes. Pour the wine into the pan and cook until almost no liquid remains, 3 to 5 minutes.
Meanwhile, heat a nonstick skillet over medium heat. Crack the egg into the pan and season with salt and pepper. Cook until the whites are firm and the middle is cooked but still runny, 3 to 5 minutes.
Transfer the mushroom hash to a plate and top with the sliced steak and then the egg.