When it comes to intense flavor of acid-based, tomato sauces, where you can choose ingredients. Avoid long cooking times (unless you must use fresh tomatoes) by just using the best prepared, unsalted sauce or paste... adding spices and ingredients during cooking... simple.
The most important technique, for the final product, to infuse flavor from the added spices, is cooling it quickly and storing it. Overnight, at least... two days is optimal. Salt must always be added at the end of the process, as it will impede cooking.
- jef Grace, Oregon