Whisk the marinade ingredients together in a small bowl.
Place the steaks in a resealable plastic bag.
Pour the marinade over the steaks. Refrigerate marinating steaks for at least 2 hours.
Remove marinating steaks from the refrigerator and let sit at room temperature for 30 minutes before grilling.
Heat the grill to medium heat. Remove steaks from the marinade and place on a hot grill.
Grill steaks for approximately 8 minutes on each side, turning only once. The internal temperature of the steak should reach 145 degrees for a medium steak (use a meat thermometer).
Heat olive oil in a heavy large saucepan over medium heat, makinng sure the olive oil doesn't turn brown. Add garlic and sauté until a light golden brown, about 5 minutes.
Add tomatoes, basil sprigs, and dried crushed red pepper to a food processor and pulse a few times. Add tomato mixture to the garlic in the saucepan.
Bring to a simmer. Reduce heat to low and simmer until mixture is reduced to a thick sauce consistency (about 3 cups), stirring occasionally, about 15 minutes.
Season sauce to taste with coarse kosher salt and freshly ground black pepper.
Top grilled steaks with tomato basil sauce. Garnish with shredded basil.