Place bacon in a cold skillet and heat over medium heat until crispy, approximately 8 minutes, then drain on paper towels.
Halve the avocado, remove the pit, and scoop the flesh into a small bowl.
Add lemon juice, salt, and black pepper to the avocado and mash with a fork until desired consistency is achieved.
Toast the bread slice until golden brown and firm.
Melt butter in a small non-stick skillet over medium-low heat and fry the egg sunny-side-up or over-easy until the white is set.
Spread the mashed avocado mixture evenly over the toasted bread.
Layer the crispy bacon strips on top of the avocado.
Carefully place the fried egg onto the bacon and garnish with red pepper flakes.