For a richer flavor, use high-quality, imported black olives. If fresh tomatoes are not available, canned diced tomatoes make a perfectly acceptable substitute. Be sure to drain them well before adding them to the sauce. The amount of anchovy paste can be adjusted to taste. Start with 1 tablespoon and add more if you prefer a stronger anchovy flavor. Fresh oregano can be substituted for dried. Use about 1 tablespoon of chopped fresh oregano. For a spicier dish, add a pinch of red pepper flakes to the sauce along with the tomatoes. If you don't have caper juice, you can substitute a splash of white wine vinegar or lemon juice. Pasta water is starchy and helps to emulsify the sauce, making it cling to the pasta better. Don't skip reserving it!