Divide the two avocados into halves and carefully remove all the seeds. Scoop out about ¼ of the flesh out of the avocados. You should have more space in the avocados for stuffing the fillings. You will need the avocado flesh for preparing the chicken salad so keep it aside.
Boil the chicken breast until it is well cooked. You can also bake it if you prefer. Slice the chicken breast into small pieces.
Chop the celery and tomato into small pieces. Dice the onion too.
Place the cooked chicken inside a mixing bowl. Add the avocado flesh, celery, onion, tomato, and the mayonnaise. Mix properly until well combined to form the chicken salad.
Fill the hollow in the avocado halves with the chicken salad mix.
Add some lemon juice. Season with pepper and salt to taste. You can also drizzle a little bit of olive oil on top of the stuffed avocados.
Best served with lettuce.