Add 2-inches of water in a pan with the lemon juice or vinegar and half of the salt and bring to a simmer (just under a boil) over high heat.
Crack an egg into a small bowl or mug and then slide the egg into the water. Repeat with all of the eggs. If water becomes to hot, reduce the temperature to keep at a simmer.
Cook for about 3 to 4 minutes until the whites are firm but the yolks are still liquified. Remove eggs with a slotted spoon and place on a plate.
Add one poached egg, lettuce, and tomato to each toast slice. Season with salt and pepper.