Place sliced onions in crock pot.
Season both sides of chuck roast with steak seasoning.
Heat olive oil in large skillet over medium high heat.
Sear each side of chuck roast until browned.
Once browned, place meat over sliced onions, then deglaze the skillet with white wine and water, scraping any bits stuck on the bottom of the pan.
Pour white white/water/drippings mixture over the beef.
In a small bowl, combine balsamic vinegar and tomato sauce.
Pour over the beef.
Cover and cook on low for 8-10 hours. It is done when it is fork tender and basically just falls apart. Enjoy!