1. Prepare the Caprese Mixture:
- In a medium bowl, gently combine the diced ripe tomatoes, cubed fresh mozzarella, coarsely chopped fresh basil, 1 minced garlic clove, and 1 tablespoon of olive oil.
- Season lightly with salt and ground black pepper. Toss gently to coat all the ingredients.
- Cover the bowl and refrigerate while you prepare the steak and assemble the rest of the salad. Chilling allows the flavors to meld.
2. Prepare and Marinate the Steak:
- Preheat your outdoor grill (or indoor grill pan/skillet) for medium-high heat. Lightly oil the grill grate once hot.
- Pat the flank steak dry with paper towels.
- Place the steak in a large resealable plastic bag or a shallow dish. Add the other minced garlic clove, 1 tablespoon olive oil, and season generously with salt and pepper.
- Seal the bag (pressing out air) or cover the dish. Massage the oil, garlic, and seasonings over the entire steak. Let it marinate at room temperature for at least 15-20 minutes while the grill preheats, or longer in the fridge if time allows (up to a few hours).
3. Grill the Steak:
- When the grill is preheated, place the marinated flank steak on the hot, oiled grates.
- Grill to your desired degree of doneness. For medium-rare (internal temperature of 140°F / 60°C before resting), cook for about 5 minutes per side. Adjust time for thickness and preference.
- Use an instant-read thermometer inserted into the thickest part of the steak to check for doneness accurately.
4. Rest and Slice the Steak:
- Once cooked, remove the steak from the grill and transfer it to a clean cutting board.
- Let the steak rest, loosely tented with foil, for at least 5-10 minutes. This is crucial for keeping the steak juicy!
- After resting, thinly slice the flank steak against the grain.
5. Assemble the Salads:
- Divide the butter lettuce mix evenly onto four serving plates or into a large salad bowl.
- Drizzle each portion of lettuce with about 1 1/2 teaspoons of balsamic vinegar and 1 1/2 teaspoons of olive oil (or whisk these together first and then drizzle). Toss the lettuce gently if desired.
- Arrange the thinly sliced grilled flank steak attractively over or alongside the dressed lettuce.
- Spoon the chilled Caprese mixture (tomatoes, mozzarella, basil) evenly over each salad.
6. Serve:
- Serve the Grilled Flank Steak Caprese Salads immediately. Enjoy this fresh and flavorful meal!