Step 1Slice garlic with sharp knife into about 5 slices lengthwise. Make a pile of slices and cut through them lengthwise again, then crosswise to mince. Set aside.
Step 2Whisk together garlic, mayonnaise, brown sugar, rice vinegar and salt in bowl until smooth.
Step 3Cut off and discard root end (about 1/4 inch) of green onions and 2 to 3 inches coarse green tops. Thinly slice green onions. Cut tomato into about 6 slices and stack slices in 2 or 3 piles. Cut into bite-size pieces.
Step 4Combine onions, tomato and ground beef in medium mixing bowl. Add 1/2 of garlic mixture and mix thoroughly until well combined.
Step 5Cook ground beef mixture in skillet set over medium-high heat, stirring constantly until beef loses its redness and is lightly browned, about 3 to 5 minutes.
Step 6Place lettuce leaves on work surface. Spread 1 1/2 teaspoons remaining garlic mixture on each leaf. Place 3 or 4 tablespoons ground beef filling in center of each leaf and roll up. Serve 2 lettuce leaves to a plate, rolled side down.