- Butterfly the steak. Using a sharp knife, slice the steak horizontally through the middle, until only about ½ inch is left. Fold it open and lay it flat.
- Pound to an even thickness. Cover the steak with parchment or wax paper then use a meat mallet or hefty rolling pin to pound it to an even thickness (¼-½ inch). This is a great time to get out some of that holiday stress!
- Season. Sprinkle the steak evenly with salt, pepper, and rosemary on both sides. Allow it to rest while you prepare the filling.
- Sauté spinach. Heat the oil in a skillet over medium heat. Add the pepper flakes and the garlic into the oil. Sauté until fragrant, about 30 seconds. Add the spinach and allow it to wilt, for about 2-3 minutes. Sprinkle lightly with a little Kosher salt then remove the mixture from the heat. Place the spinach mixture in a paper towel and squeeze gently (be careful, it's hot!) to release any excess moisture.
- Mix filling. Add the spinach to a bowl and stir in chopped tomatoes, feta cheese, and lemon zest. Set aside.
- Fill the steak. Place the steak so the grain is running horizontally in front of you. Spread the feta mixture all over the top of the steak, leaving just a small edge. If you have edges that are torn or very thin, trim them off.
- Roll and freeze. Roll the steak over the filling tightly from bottom to top. Wrap it with saran wrap and freeze for 15 minutes. This makes for easier slicing.
- Wrap and slice. Once the steak has chilled, remove the saran wrap and preheat the oven to 375 degrees. Wrap a piece of butcher’s twine in the very center of the roll, then add more on either side, spacing each tie 2-2.5 inches apart. You want the twine to be in the center of each slice. Use a sharp knife to slice the steak. You should get 7-8 pieces.
- Sear then bake. Heat vegetable oil in a large oven-safe skillet over high heat until it shimmers. Add the steak, filling side down, and brown for about 2 minutes. Flip and brown the other side, for another 2 minutes. Pop the whole pan into the oven and bake for another 5-9 minutes. Place a meat thermometer at the thickest part of the interior of the roll. Remove it around 145 degrees for a perfect medium.
- Rest and serve. Rest the steak for 10 minutes, then top with balsamic glaze before serving.
Beef Pinwheels can be left at room temperature for up to 2 hours, then should be refrigerated in an airtight container for up to 5 days.
To make ahead, follow the instructions through step 7. Instead of freezing, store the beef in the fridge for up to 24 hours before slicing and searing.
Leftover roll-ups can be reheated in a 390 degree air fryer for 5-7 minutes.