Combine tomato, Parmesan cheese, basil, garlic, vinegar and 1 teaspoon olive oil in a small bowl. Set aside.
Gently shape ground beef into 4 half¬inch-thick burgers. Season burgers on both sides with 1 tablespoon seasoning.
Grill over direct medium heat (350° to 450°F) with the lid closed as much as possible, until the internal temperature reaches 160°F for medium, 12 to 15 minutes, turning once.
Lightly brush both sides of the sourdough bread with olive oil. Grill for 3 to 4 minutes, turning once, until bread is lightly toasted. Place burgers ?on bread; top with tomato mixture and additional slice of bread.
Balance out these delicious flavours with the classic Weber® Gourmet Burger Seasoning.