This salad is very, very simple, so the ingredients must be of the absolute best quality.
What you will need:
--A perfectly ripe avocado or two. It must not be overripe or it will disintegrate, but unripe avocados are horrible. So get one that is still firm, but slightly soft. The Hass variety with the bumpy black skin is the best.
--A real tomato or two. This is really the hard part. The only way you can be sure you have a real tomato is to grow it yourself (see Inyo's writeup on growing tomatoes), but if that's not possible, you might be able to find one at a farmer's market or a roadside stand somewhere.
You will not find a real tomato in any kind of supermarket. This is one of the tragedies of our time, but it's best not to dwell on these things. Instead, hope for a better future and plant some seeds or something.
Meanwhile, look for a tomato that is red and has that distinctive, intoxicating tomato smell.
--A lime or two. The sweeter, the better, since the tomatoes are acidic as well.
--Salt. Kosher salt is good, but not strictly necessary.
--Pepper. Fresh ground pepper, of course--if you use the other kind you might as well just put vacuum cleaner dust on your food.
Dice the tomatoes and avocados, put them in a bowl, squeeze the lime juice over them, and season with salt and pepper. If you want to get all fancy, add just a little nutmeg. If it seems too acidic, add a tiny bit of sugar.
Eat out on the veranda.