In a food processor, combine the onion, 1/4 cup (60 ml.) water, 1 tbsp. pomegranate molasses, the olive oil, salt, and pepper and process until puréed. Transfer to a bowl and stir in the dill. Add the pork and stir to coat well. Cover and refrigerate overnight or up to 2 days.
About 1 hour before serving, thread the pork onto 4 metal skewers, each about 10 in. (25 cm.) long; discard the marinade. Let the skewers stand at room temperature 30 minutes.
Light a medium fire in a charcoal or gas grill, or position an oven rack about 5 in. (5 cm.) from the heating element and preheat the broiler. Lightly oil the grill rack or oil the rack on a broiler pan.
Meanwhile, in a small bowl, stir together the remaining 3 tbsp. (45 ml.) pomegranate molasses and 2 tbsp. water.
Place the skewers on the grill rack directly over the fire, or on the broiler pan and slip under the broiler, and cook, turning the skewers occasionally, until the pork is cooked and charred at the edges but still juicy within, about 15 minutes. Toward the end of cooking, brush on a bit of the diluted pomegranate molasses to glaze.
Serve the skewers with the remaining diluted pomegranate molasses for dipping and accompany with the onion-parsley salad.
*Traditionally, pomegranate molasses is made from fresh pomegranate juice cooked down to a syrup with lemon juice and sugar; concentrate is simply fresh pomegranate juice brought to a boil, then simmered until reduced. They are interchangeable in most recipes, Wolfert says. Now that she's on a low-sugar diet, she prefers the concentrate.