Step 1
Preheat the oven to 375 degrees F (190 degrees C).
Step 2
Bring chicken stock and bay leaves to a boil in a large saucepan. Reduce heat and simmer while preparing the other ingredients. Taste stock; it should taste a little over-salted. Season with 1 to 2 teaspoons salt and 1 teaspoon black pepper as needed.
Step 3
Season chicken with salt and pepper.
Step 4
Squeeze out seeds from each tomato half over a sieve and into a bowl. Reserve the juice and discard the seeds. Grate the cut sides of the tomatoes over a bowl through the large holes of a box grater. Discard the skin. Combine the tomato juice and the grated pulp.
Step 5
Heat a large skillet over medium-high heat for 2 to 3 minutes and coat with 1 tablespoon olive oil. Add chicken in batches in a single layer with space between pieces. Saute until meat is mostly opaque about 4 minutes; it will continue cooking in the oven. Place chicken in a 9x13-inch baking pan. Repeat with the remaining chicken being careful not to burn the fats rendering in the skillet.
Step 6
Add 2 tablespoons olive oil to the same skillet. Add the tomato juice-pulp mixture. Cook scraping up browned bits from the bottom of skillet until juices are mostly evaporated about 5 minutes. Add 2 teaspoons salt 1 teaspoon black pepper and paprika. Mix well. Add onions and garlic; saute until is fragrant about 3 minutes. Stir the mixture called a sofrito into the baking pan with the chicken.
Step 7
Heat the last tablespoon of olive oil in the hot skillet. Add green beans and saute for 1 minute. Add bell peppers; saute until green beans are crisp-tender about 2 minutes more. Transfer mixture to the baking pan and stir well; mix in quinoa and saffron.
Step 8
Remove and discard bay leaves from stock and bring to a boil. Pour 1/2 into the baking pan. Mix carefully until well combined. Add remaining stock and stir carefully. Lay rosemary sprigs on top.
Step 9
Bake in the preheated oven until quinoa is tender yet firm to the bite 35 to 45 minutes.