Rinse the chicken, remove any excess fat from around the vent, and pat dry with paper towels. In a small bowl, mix together the garlic, 1 teaspoon salt, paprika, and vinegar. Use this mixture to rub all over and inside the cavity of the chicken. Cover the chicken and let it sit on a platter for 1 hour.
Heat a large cast iron skillet over medium high heat and add the olive oil. Shake the chicken from both ends to drain off the excess vinegar. Using kitchen tongs and a large wooden spoon to steady the bird, brown it on all sides in the hot oil. This will take a good 10 to 15 minutes.
Preheat the oven to 350 degrees. In a large enamel and cast iron casserole, combine the tomatoes, onions, butter, 1/2 teaspoon salt and the black pepper. Add 1/2 cup water and set the chicken on top of this mixture.
Roast the chicken for 20 minutes per pound, or until the thigh meat is done through with no trace of pink remaining. Transfer the chicken to a warm serving platter and cover loosely with aluminum foil, while you tip the casserole to one side and spoon off the excess fat. Carve the chicken into serving pieces as desired, and serve with some of the vegetables from the pan, sprinkled with the parsley.