In a medium bowl, whisk together olive oil, minced garlic, lemon juice, salt, and pepper to create a flavorful marinade. Coat the flank steak thoroughly with this mixture, cover and let it marinate for at least 30 minutes at room temperature, or for 2-4 hours in the refrigerator for maximum flavor.

While the steak is marinating, combine fresh basil leaves, pine nuts, minced garlic, Parmesan cheese, lemon juice, and olive oil in a food processor. Pulse until smooth yet textured, adjusting seasoning with salt and pepper to taste.

Preheat your grill to medium-high heat, around 400–450°F (200–230°C), ensuring the grates are clean and lightly oiled.

Place the marinated flank steak on the grill and close the lid. Grill for about 4-5 minutes on each side for medium-rare, adjusting the time based on your desired doneness.

Remove the steak from the grill and let it rest for 5-10 minutes before slicing against the grain into thin strips.

On a serving platter, arrange the sliced flank steak, top with burrata, and drizzle the pesto over the steak. Garnish with toasted pine nuts if desired.