8 leaves from 1 medium head butter lettuce, such as Boston or Bibb
6 slices bacon (about 6 ounces)
2 tablespoons mayonnaise
1 tablespoon finely chopped chives
1 tablespoon freshly squeezed lemon juice
1/8 teaspoon freshly ground black pepper
1 pint cherry or grape tomatoes, halved
1 medium avocado, diced
Arrange a rack in the lower third of the oven and heat to 400°F. Lined a rimmed baking sheet with parchment paper or aluminum foil.
Lay the bacon on the baking sheet in a single layer. Bake until deep golden-brown and crispy, 15 to 20 minutes. Remove from the oven and let cool. Meanwhile, stir the mayonnaise, chives, lemon juice, and pepper together in a small bowl; set aside.
Once the bacon is cool, transfer it to a cutting board and coarsely chop it. Fill each lettuce leaf with tomatoes, bacon, and avocado. Drizzle with the dressing and serve immediately.
Make ahead: The bacon can be cooked and chopped a day ahead of time. Store it in an airtight container in the refrigerator.