01 - Bring a small pot of water to a rolling boil. Gently lower the eggs into the water and cook for 9 to 10 minutes for a firm hard-boiled center. Transfer eggs to a bowl of cold running water to cool, then peel and slice into rounds.
02 - While the eggs cook, toast the bread slices in a toaster or on a skillet until golden brown and crisp on the edges.
03 - Halve the avocado and remove the pit. Scoop the flesh into a mixing bowl and mash with a fork along with the lemon juice, salt, and freshly ground black pepper until smooth and creamy.
04 - Divide the mashed avocado evenly between the two toasted bread slices, spreading it in an even layer across each slice.
05 - Arrange the thinly sliced tomato over the avocado layer, then place the sliced hard-boiled egg on top. Drizzle with olive oil if desired.
06 - Finish with a sprinkle of fresh chives or parsley and crushed red pepper flakes for a touch of heat. Serve immediately while the toast is still warm and crisp.