Place the bitter orange juice in a mixing bowl along with the black pepper, allspice and salt; mix well. Stir in the red onions and bay leaves.
Char or broil the pepper under the broiler, on the grill, on a hot comal, or in a dry skillet set over medium heat, turning once or twice, until the skin is lightly charred, 3 to 6 minutes.
Add the pepper, without removing the charred skin, to the onion mixture and toss well to combine. Marinate at room temperature 30 minutes to 2 hours, then store, covered, in the refrigerator.