Preheat oven to 325°F
Place tomatoes in boiling water, after cutting an X in the bottom of each tomato. Leave in water for about 1-2 minutes, until skin starts to fall away. Let tomatoes cool, then peel. Cut the sides and top off the tomato, clear out seeds. Chop tomatoes and set aside.
Grill sausage and chicken thighs, or cook on grill pan until mostly done. Cut sausage into 1 inch slices and chicken thighs into thirds.
Heat ¼ cup of the olive oil in a large sauté pan over medium heat. Cook onion until translucent, about 4 minutes. Add garlic, stir and cook for 2 minutes, until garlic is lightly golden; scrape grated tomato into pan. Stir in sherry and reduce heat to medium-low. Cook for 20 to 22 minutes, stirring frequently in final 10 minutes to prevent burning, until mixture is very thick, noticeably darker and tomatoes have caramelized. Remove to a bowl and set aside.
Add sausage into pan and sprinkle rinsed, soaked rice over sausage in pan. (Add more oil if you would like at this point). Stir to coat rice in oil. Add reserved tomato mixture, chicken stock, thyme, rosemary, paprika and saffron; stir to evenly distribute rice and chorizo. Season with salt and pepper. Lay chicken in a single layer over rice. Increase heat to high, bring to a vigorous boil and cook for 3 minutes, shaking pan, but don’t stir.
Cover with foil, place in oven and cook for 12 minutes. Remove foil, sprinkle with peas and roasted red pepper. Cook, uncovered, for 3 minutes. Let rest for 5 minutes before serving.
See Shrimp & Sausage Paella Recipe for alternate cooking method.