Using the flat side of a chef’s knife, crush cardamom pods and remove the black seeds. Discard pods. Transfer black seeds to a mortar and pestle along with peppercorns, allspice berries, cloves and fennel seeds. Grind into a coarse powder. Stir in salt.
Pat pork dry with paper towels. Brush pork with 2 tablespoons honey. Pat spice mixture all over pork. Cover with plastic wrap and refrigerate overnight. Let meat return to room temperature before roasting.
Preheat oven to 450°F.
Set pork loin on a rack in a roasting pan. Brush or spray with olive oil and season with salt and freshly ground black pepper.
Roast in center of oven for 10 minutes. Reduce oven temperature to 350°F and continue to roast for 55-60 minutes longer, or until an instant-read thermometer registers at 145°F.
Transfer pork loin to a platter and tent with foil. Let rest for at least 10-15 minutes before carving.