These sandwiches are wonderful as is, though you can certainly layer on some sliced turkey or sharp cheddar if you like. Pick up the best ingredients, juicy heirloom tomato, fresh lettuce, and good-quality bacon, to ensure the fullest flavor in this classic sandwich. Serves four
1in a small bowl, mash the flesh of one of the avocados with lemon juice and 1/4 teaspoons salt. Taste and season the avocado with more lemon juice and salt if needed. Put the tomato slices on a large plate, drizzle with 1 tablespoon of the oil and sprinkle with 1/2 teaspoons salt.
2In a large heavy skillet, like cast iron, cook the bacon with the remaining 1 tablespoon oil over medium heat, flipping occasionally, until it browns and renders much of its fat, 5 to 10 minutes. Transfer the bacon to a plate lined with paper towels. Add the onion rounds to the skillet, sprinkle lightly with salt, and cook until they start to Brown, about two minutes. Flip and cook until the other side is Brown but the onion is still firm, about another two minutes. Remove from heat.
3For each sandwich, spread some of the mashed avocado on one slice of bread. Layer onto tomato slices, to onion rounds, the bacon, lettuce, and avocado slices. Top with the remaining slices of bread and serve.