What makes Puerto Rican food so amazing? It's that sofrito.
Sofrito is the basis of almost any Puerto Rican dish (also know as comida criolla). Any good Puerto Rican household has a container of sofrito in its fridge. Goya sells it by the bottle full, however I prefer to make it from scratch. In my fridge, the sofrito is usually stored in a random "I Can't Believe It's Not Butter" container.
Traditionally, sofrito is made from recao (culantro) and aji dulce (little sweet peppers), yellow onions, garlic, tomatoes and cilantro. Being that I live in Pittsburgh and don't have access to some of these ingredients, I improvise by simplifying the traditional recipe and just use cilantro, tomato, a red and green pepper, a yellow onion and garlic. Add all these items to a food processor and puree away!
To cook with sofrito, take a few tablespoons and saute it in some olive oil. I like to add some fresh chopped onion (for added sabor), olives, capers and achiote (seeds from a shrub native to the Americas, it adds a subtle flavor and a beautiful red color to food). You can also add bacon, salted pork or cured ham (if you are not a vegetarian).
Once you have all those ingredients assembled anything you cook using your sofrito with have a definitive Puerto Rican flavor. My recommendation would be to use it when cooking beans, stews or even seasoning meats. It's such an easy way to give a dish so much flavor!
Buen Provecho! Enjoy your food!