Pollo Guisado (Puerto Rican Chicken Stew)

For the sofrito, in a blender, process the tomatoes until finely chopped. Add the onion and garlic and process until finely chopped and incorporated. Add the bell pepper, cilantro and culantro (if using) and process until the mixture is well combined and mostly smooth.  
 
You can use the sofrito immediately, cover it and store it in the refrigerator for up to 1 day or pour it into an ice cube tray and freeze for up to 6 months. 

For the pollo guisado, add the canola oil to a large heavy-bottomed pot and place over medium-high heat. Season the chicken with sazon and adobo, add the chicken and sear for 3 to 5 minutes, or until golden brown. Add the onion and cook for 2 to 3 minutes, or until translucent. Season with salt and add the tomato sauce and sofrito. Stir in the water, olives (if using), potato pieces and carrots and then scrape the bottom of the pot with a wooden spoon to loosen all the brown bits. Turn the heat to low and let simmer, partially covered, for 1 hour, keeping an eye on it because the potato will thicken the broth and you might need to add more water. 

Season with salt and pepper. Serve the guisada over rice.