2 medium onions, halved and thinly sliced (about 4 cups)
1 to 1 ¼ cup reduced-sodium beef broth
5 Tablespoons balsamic vinegar
2 Tablespoons Worcestershire sauce, or more to taste
Season steak all over with 3 teaspoons Dash Table Blend and ground black pepper to taste. Set aside and allow it to come to room temperature while preparing the onions.
Preheat oven to 400 degrees.
Warm a large heavy-bottom skillet over medium-high heat. Add 2 teaspoons of oil and sear the steak for 2 to 3 minutes on the first side until well browned. Then flip with tongs and sear the other side for about 2 minutes or until well browned. Remove pan from the heat and transfer steak to a baking sheet.
Wipe off any residual burnt oil on the skillet with a paper towel. Warm the same skillet over medium heat, add the remaining oil and sliced onions. Sauté 2 to 3 minutes or until they begin to soften slightly. Add 1 cup of the broth, the balsamic vinegar and Worcestershire sauce, scraping the bottom of pan with a wooden spoon or spatula to incorporate any brown bits. Cook over medium heat for 20 to 25 minutes, stirring frequently, until the onions are soft and the liquid has reduced to 2/3. Add additional broth if needed.
When the onions are halfway cooked, place steak (on the baking sheet) in the preheated oven for 6 to 8 minutes, or until the steak reaches the desired temperature. (I remove my steak at about 135 to 140 degrees for medium doneness, allowing for carryover cooking time.) Once steak is cooked to your liking, remove it from the pan, tent with foil, and allow to rest for 10 minutes.
Add any reserved juice on the baking sheet that was generated from the steak to the cooked onion mixture. Slice steak thinly against the grain and serve with balsamic onions on top or on the side.