Adjust oven rack to middle position and heat oven to 475 degrees. Spread 1/4 cup mayonnaise over both sides of bread slices and transfer to baking sheet. Bake until golden brown, 8 to 10 minutes. Let cool 5 minutes, then cut into 1-inch croutons.
Cook bacon in large skillet over medium heat until crisp, about 8 minutes. Transfer to paper towel-lined plate. Discard drippings.
Whisk remaining mayonnaise and vinegar in large bowl. Add bacon, tomatoes, lettuce, and croutons and toss to combine. Season with salt and pepper. Serve.
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