Phil's recipe is fine, but start by discarding all the quantities in any sense of precision. You want basil, garlic, onion, and tomato, and of course salt and pepper. Peel and seed the tomatoes, and dice. Dice the onion. Mince the garlic and the basil. Mix these things as looks more or less good to you, and add salt and pepper to taste. Now taste. What do you need more or less of? When the balance seems right, add good olive oil and dump it on toast rounds.
Now let's suppose the basil looks horrible. How does the cilantro look? How about sage?
Suppose the tomatoes are waxy and flavorless. Okay, let's try... beets! Okay, beets go well with sage, and maybe a little caraway seeds. Fine, mix that up, and you've got another classic.
How about a can of garbanzo beans? Add a little sage or rosemary or something, and lots of garlic, and a fair bit of onion, and go from there.
And on and on.
This is not a recipe sort of thing. It's a "what have I got? what's fresh? what's appealing?" kind of thing. Chop up a main thing, add a complementary herb, add some alliums (onion, shallot, garlic, whatever) to bring up the sharpness, add salt and pepper to give a perfect balance and accent to everything, and add olive oil to round it all out. Heave it on toast rounds: French, Italian, German, whoever. Try toasted lavash bread -- what's the harm?