Prepare the Flank Steak:

1. Butterfly the Steak: Place the flank steak on a cutting board. Using a sharp knife, carefully slice the steak horizontally (without cutting all the way through) and open it like a book.
2. Pound to Even Thickness: Cover with plastic wrap and use a meat mallet or rolling pin to pound the steak to about ¼-inch thickness for even cooking.
3. Season the Meat: Rub both sides of the steak with olive oil, salt, pepper, oregano, basil, and garlic powder.

Prepare the Filling:

4. Sauté the Spinach: Heat 1 tablespoon olive oil in a pan over medium heat. Add garlic and cook for 30 seconds until fragrant. Add spinach and cook until wilted (about 2 minutes). Remove from heat and let cool slightly.
5. Mix the Filling: In a bowl, combine the sautéed spinach, sun-dried tomatoes, mozzarella, Parmesan, and red pepper flakes.

Stuff and Roll the Steak:

6. Spread the Filling: Evenly spread the spinach mixture over the prepared flank steak, leaving a small border around the edges.
7. Roll Tightly: Starting from the short end, tightly roll the steak into a log. Secure with kitchen twine at 1-inch intervals.

Sear and Bake:

8. Sear the Steak: Heat a large oven-safe skillet over medium-high heat. Add 1 tablespoon olive oil and sear the steak on all sides until browned (about 2 minutes per side).
9. Bake: Transfer the skillet to a preheated oven at 375°F (190°C) and bake for 30-40 minutes, or until the internal temperature reaches 130-135°F (55-57°C) for medium-rare or 140-145°F (60-63°C) for medium.
10. Rest & Slice: Remove from the oven, tent with foil, and let rest for 10 minutes before slicing into medallions.

Optional Sauce:

11. Make the Sauce: In a saucepan, heat olive oil and sauté garlic until fragrant. Add crushed tomatoes, Italian seasoning, salt, and pepper. Simmer for 10 minutes.
12. Serve: Drizzle over the sliced stuffed steak or serve on the side.