Heat a large cast iron skillet over medium high heat. Add bacon and cook until brown and crispy, about 6-8 minutes. Transfer to a paper towel-lined plate; set aside.
Place eggs in a large saucepan and cover with cold water by 1 inch. Bring to a boil and cook for 1 minute. Cover eggs with a tight-fitting lid and remove from heat; set aside for 8-10 minutes.
Cool eggs in a bowl of ice water for 2-5 minutes. Drain well and peel; cut the eggs in half lengthwise, reserving the yolks.
In a small bowl, mash the yolks and avocado with a fork until chunky. Stir in cilantro, lemon juice and lemon zest; season with salt and pepper, to taste.
Use a pastry bag to pipe into the eggs, topped with bacon and garnished with chives and cayenne pepper, if desired.