In a bowl, dissolve the salt with the lemon juice and water.
Add the olive oil and whisk until well emulsified.
Stir in the chopped garlic, oregano and parsley, if using, and a few rounds of freshly ground pepper. Whisk to re-emulsify before serving.
Storage
Keep refrigerated in an airtight container for up to 2 weeks.
Variations
Jar Method: Shake ingredients vigorously in a closed jar in the same order as instructed above. Shake to re-emulsify before serving.
Garlic - Pound to a smooth purée with a pestle, or by scraping it with a slanted wide blade of a knife.
Parsley - Use on its own as a great substitute for oregano.
Mint - Add a handful of fresh spearmint as an addition to, or substitute for, oregano. Peppermint has a stronger flavor. Experiment to see which you like best.
Dill, fennel fronds, rosemary or cilantro can be used as a substitute for oregano.
A touch of hot chili powder or flakes, although not traditional, will work for all you hot and spicy lovers.
Capers - With firm, dense fish like swordfish or tuna. Note, capers can easily overpower more delicate fish such as sea bass.
Dijon mustard - A nice touch, and can help keep the sauce emulsified longer. Mix in before adding the oil.