Sofrito is cooked onions, peppers, cilantro, tomato, and garlic. There can be a few differences, but that's the basics of it.
I don't make sofrito ahead of time and puréed, but rather when I'm making a dish I incorporate the elements.
In any case, you should make Latin-style (as opposed to Spanish) arroz con pollo. I never make arroz con pollo the same way, so I can't exactly give you a recipe. Dominican style is called locrio and includes tomato. For what a lot of people consider arroz con pollo, though, you'll want to use annatto oil. First you season your cut up chicken, brown it in a hot pan, set it aside, pour out any excess fat in the pan, and pour in some annatto oil. Toss some sofrito in there and sauté until aromatic, then put your rice in and coat with the oil. Pour in your liquid (water or stock) --- same amount of liquid as rice no matter how much people tell you it's 2:1.
Bring to a boil, put the chicken pieces back in, and season well (liquid for rice needs to be well salted, you need about a tablespoon of kosher salt for four cups of rice) and when the level of the water meets the rice, get the heat as low as possible, cover tightly, and let steam for 30 minutes. Garnish with freshly chopped cilantro or parsley, or scallions.
That's just a rough outline. I do this depending on my mood and adding as I go along. Sometimes there's wine, sometimes there's tomato, and so on.
Daisy Martinez is good for sofrito recipes. She also has recipes for beans that are cooked basically like we do it in the DR (but she puts meat in hers, while ours are vegan most of the time).
If you don't want to make annatto oil, you can sauté some ground annatto in olive oil, or turmeric. If you have saffron, you can of course use it and it will be delicious.