Begin by butterflying the flank steak. Place the steak on a cutting board, and carefully slice it horizontally, stopping just before you cut all the way through. Open it up like a book, and gently pound it to an even thickness, about 1/2 inch thick.
In a skillet over medium heat, add the oil. Once hot, sauté the chopped onion until translucent, about 3-4 minutes. Add the minced garlic and cook for an additional minute until fragrant. Stir in the baby spinach and cook until wilted, about 2-3 minutes. Remove from heat and let it cool slightly.
In a mixing bowl, combine the sautéed spinach mixture with the cream cheese and half of the provolone cheese. Season with salt and pepper to taste. Mix until well combined.
Spread the filling evenly over the butterflied flank steak, leaving a small border around the edges. Sprinkle the remaining provolone cheese on top of the filling. Starting from one end, carefully roll the steak tightly into a log. Secure it with kitchen twine or toothpicks at intervals.
Preheat your oven to 375°F (190°C). Place the rolled flank steak in a baking dish and cover with aluminum foil. Bake for 25-30 minutes. For a nice crust, uncover and broil for an additional 3-5 minutes until the outside is browned and crispy.
Remove from the oven and let the rolls rest for about 5 minutes before slicing. Cut into 1-inch thick pieces and serve warm. Enjoy your Spinach Cheese Stuffed Flank Steak Rolls with a side salad or your favorite vegetables.
