Serves 4 as a main course, or 8 as an appetizer
For the pickled red onions:
1 cup cider vinegar
3 tablespoons sugar
1 tablespoon salt
1 bay leaf
5 allspice berries
5 whole cloves
2 small, dried chile peppers
1 large red onion, peeled and thinly sliced into rings
1/3 cup pomegranate seeds, plus more for garnish
chopped parsley, for garnish
For the Bone Marrow:
2 6-inch (about 6 pounds) long beef or veal marrow bones cut in half, lengthwise
Toast, for serving
To prepare pickled red onions: Heat the vinegar, sugar, salt, bay leaf, cloves, allspice and chile in a small nonreactive saucepan, until boiling. Add the onion slices and lower the heat to low, then simmer gently for 30 seconds. Remove from heat and cool completely. Transfer the onions and liquid to a container. Cover and refrigerate until cool, at least 1 hour. Fold in pomegranate seeds.
To make bones: Place bones in a large bowl and cover with cold water. Keep covered in the refrigerator and soak for at least 30 minutes, and up to 24 hours, changing water every 8 hours.
Preheat oven to 400 degrees F. Dry bones with paper towels. Place bones, cut side up, on a baking sheet. Roast until bone marrow is soft and begins to separate from the bone but before it begins to melt, 15-20 minutes. Sprinkle bones with pomegranate seeds and parsley. Spread bone marrow onto toast and top with pickled onions.