Preheat oven to 350°F.
Using a meat mallet, pound round steaks to ½-inch thickness. Cut into even servings, about 4-6 ounces each.
Dredge the steak cutlets in seasoned flour, coating it evenly. Shake off any excess flour.
Heat 2 tablespoons of the oil in a large ovenproof skillet or Dutch oven over medium-high heat. Working in batches and adding a tablespoon of oil between batches, sear the coated steaks on both sides, about 2-3 minutes per side. Transfer the browned steaks to a plate and set aside.
In the same skillet, add the remaining oil, chopped onion and carrots. Add ¼ cup water, and scrape up any solid bits from the bottom of the pan. Sauté until the vegetables are softened, about 5 minutes.
Season the vegetables with seasoning salt or salt and black pepper.
Add the diced tomatoes (with juices), Worcestershire sauce, and beef broth to the skillet. Stir to combine. Add additional seasoning if desired.
Return the browned steaks to the skillet, nestling them into the sauce and vegetables.
Cover the skillet or Dutch oven with a lid or aluminum foil. Place in the preheated oven and bake for 2-2 ½ hours, or until the steak is tender.
Carefully transfer the pan from the oven to the stovetop.
In a small bowl, whisk together cornstarch and 1-2 tablespoons water. Over medium heat, stir the cornstarch slurry into the pan. Allow the mixture to thicken for 3-5 minutes.
Serve Swiss steak over mashed potatoes, rice, or egg noodles.