Grilled Steak With Herbs without fish butter vegetables

1/2 cup olive oil 6 tablespoons white balsamic vinegar 1 3/4 teaspoons dry mustard, divided 1 tablespoon dark brown sugar 1 2-pound well-trimmed tri-tip beef[...]

1 pound hanger, skirt, or flank steak 1 teaspoon kosher salt plus more Freshly ground black pepper 1 medium tomato (about 6 ounces), halved 1 tablespoon[...]