Season the flank steak with salt and black pepper on both sides.
In a small bowl, whisk together olive oil, balsamic vinegar, minced garlic, and honey.
Place the steak in a shallow dish and pour the marinade over it, ensuring it is well coated. Cover and refrigerate for at least 30 minutes, or up to 2 hours for more flavor.
Preheat the grill to medium-high heat.
Remove the steak from the marinade and discard the marinade.
Grill the steak for about 5-7 minutes on each side for medium-rare, or until it reaches your desired doneness.
Remove from the grill and let it rest for 5 minutes before slicing.
While the steak is resting, combine the cherry tomatoes, mozzarella, and basil in a bowl. Drizzle with a little olive oil and season with salt and pepper to taste. Toss gently to combine.
Slice the steak against the grain into thin strips. Serve topped with the Caprese mixture.