Slice the Tenderloing about 1/2 inch thick each piece and Sprinkle steaks with salt and pepper.
Heat a large nonstick pan over medium-high heat. Add the butter. When it is melted add the steaks; cook 2-3 minutes on each side or until it’s well sealed. This is good to keep the steak juicy. Put the steaks on a plate and stir into the Pan the wine and mix with all the steak remaining.
Then add the onions, tomatoes and the parsley. Mix well for 1 minute and add the mushrooms. Cook for about 5-10 minutes or until browned and the liquid evaporates a little.
Then add the steaks back to the pan. Make sure not to pile them. Let them have their own space and cover with the sauce. Let it cook for 5 more.