Prepare barbecue (medium-high heat). Mix first 3 ingredients in medium bowl. Transfer 3 tablespoons sauce to small bowl and reserve. Add meat to remaining sauce in medium bowl and mix gently. Divide meat mixture into 2 equal portions. Flatten each to 1/2� thick patty; sprinkle with salt and pepper.
Grill cut side of buns until toasted, about 1 minute. Grill patties to desired doneness, about 4 minutes per side for medium. Spread bottom half of buns with reserved sauce. Top each with burger, tomato slice, lettuce and bun top.