Today has been traditionally the first of two celebrations in honor of Saint Peter's cathedra (chair), the other taking place on February 22. In the new calendar, the feast is celebrated only on the latter date.
The Catholic Encyclopedia explains the importance of both, and gives a history of the ancient chair itself.
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What could be more appropriate for Peter the Fisherman than "Rockfish" (aka 'Striped Bass' here on the East Coast)?
BAKED ROCKFISH
You can use this recipe for either a whole fish, or fish steaks.
Finely chop 2 onions. Minced 2 garlic cloves.
If using a whole fish, clean the fish and remove the scales. Make a few slits crosswise on the top.
Preheat oven to 400 degrees F.
Pour 1/3 cup of olive oil into your baking dish. Spread half of the onion and garlic in an even layer in the dish, and lay the fish or fish steaks on top. Sprinkle with salt and pepper, the remaining onion and garlic, 1/8 cup of olive oil, 2 tablespoons of breadcrumbs, and about 1/2 cup of white wine.
Bake, allowing about 12 minutes per pound. Sprinkle fish with 2 tablespoons of parsley and a little lemon juice, and serve.