In a shallow dish, mix together 2 tablespoons of sweet rice flour, kosher salt, onion powder, garlic powder, and black pepper. Coat each cube steak with the flour mixture.
Heat 1 tablespoon of olive oil in a large skillet over medium-high heat. Add the cube steaks and sear for about 2-3 minutes on each side. Transfer the steaks to a plate and keep them warm.
In the same skillet, add the remaining 1 tablespoon of olive oil along with the sliced onions, mushrooms, and dried thyme. Cook until the onions are translucent (about 6-8 minutes). Remove the veggies from the skillet and set them aside with the steaks.
Reduce the heat to medium and melt the butter in the skillet. Add the remaining 2 tablespoons of sweet rice flour and whisk for about 1 minute to form a light roux. Gradually pour in the beef broth while whisking. Add the Worcestershire sauce and simmer until it thickens enough (about 6 minutes).
Return the cube steaks and the onion-mushroom mixture to the skillet with the gravy. Cover and simmer for an additional 5 minutes. Adjust seasoning.
Serve the cube steaks with gravy over the top. Garnish with chopped fresh parsley.