In a shallow dish, mix together 2 tbsp of sweet rice flour, 1/2 tsp kosher salt, 1/2 tsp onion powder, 1/4 tsp garlic powder, and 1/4 tsp black pepper. Coat each cube steak with the flour mixture.
Heat 1 tbsp 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 unsalted butter in the skillet (we want to make the most out of that skillet!). Add the remaining 2 tbsp 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 (around 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.