Heat the olive oil in a skillet over medium-high heat. Add steak and brown well on both sides. Salt and pepper to taste then transfer to a slow cooker.
Add the sliced onion to the skillet and cook till slightly browned and beginning to turn translucent, about 2 minutes. Place it on top of the steak in the slow cooker.
Sprinkle meat and onions evenly with thyme, salt and pepper then pour the tomato sauce over the top. Add the water to the skillet.
Bring to a boil and whisk up all of the browned bits from the bottom of the pan. Cook until liquid is reduced by half then add this mixture to the slow cooker.
Cover and cook on LOW for 8 to 10 hours. Serve and enjoy!!