Crack the egg open into a bowl. Add water to a saucepan and bring to a boil.
Once the water is boiling add the egg and leave to cook for two minutes. Remove from heat and leave to simmer for ten minutes and use a slotted spoon to remove it from the water on to a paper towel.
Meanwhile, peel avocado and remove the seed.
Add the avocado to a plate, mash until smooth and add a pinch of salt and pepper.
Spread the avocado on each slice and add tomatoes and egg as shown.
Notes
Eggs: Feel free to make this recipe with your preferred choice of eggs.