1Heat oven to 400°F. Line sheet pan or shallow baking pan with foil; place wire baking or roasting rack in pan. Arrange bacon slices over rack. Bake 10 to 15 minutes or until bacon is crisp. Cool.
2Meanwhile, in medium bowl, beat pancake mix and water with whisk until smooth. Follow directions on pancake mix box to make 6 (4-inch) round pancakes. Cool.
3Thinly slice half avocado; place slices on plate. Coat each slice with lemon juice to prevent browning. Set aside.
4To make sandwiches, spread each of 3 pancakes with desired amount of mayonnaise. Divide avocado slices among pancakes. Break bacon slices in half; place over avocado. Top with seasoned tomato slices and lettuce. Spread remaining 3 pancakes with mayonnaise; place mayonnaise side down over lettuce to make sandwiches.