Heat oven to 400°F. Season chicken liberally with salt, pepper, and paprika.
Heat oil in an 8-qt. saucepan over medium-high heat. Working in batches, add chicken, skin side down, and cook until skin is golden brown, about 6 minutes. Transfer chicken to a large roasting pan, skin side up, and set aside.
Return pan to heat and add garlic, peppers, and onions; cook, stirring, until vegetables begin to soften, about 8 minutes. Stir in tomato paste, cook for 1 minute, and then add chicken stock; scrape browned bits off bottom of pan and mix. Pour vegetables and stock around chicken, and bake until chicken is browned and cooked through, about 1 hour.