Rinse fillets & gently pat them dry with a paper towel. Cut each fillet in half crosswise to make four pieces of fish, about equal in size. In a small bowl, combine olive oil, cumin, salt & pepper. Brush both sides of the fillets with the mixture; cover and refrigerate about 30 minutes to 1 hour. Prepare a mediumhot fire in a charcoal or gas grill. Prepare the Mediterranean Skillet Sauce (below) as the grill preheats. Lay the lemon slices on the oiled grill, using four slices to make a square large enough to hold a piece of fish. Repeat with remaining slices to make four squares in all directly over the coals. Set a piece of fish on top of each lemon square. Cover & grill, without turning, for a total of 6 to 8 minutes or until the fillets are opaque in the center. To test for doneness, make a small incision with the tip of a sharp knife to peek into the center of each fillet. Remove the fish to individual platters by sliding a wide metal spatula under the lemon slices & picking up fish at the same time. Gently pull the lemon slices out from under the fish, inverting them on the platter, grilled side up. They will have a bronzed, slightly caramelized look. Spoon equal amounts of the Mediterranean Skillet Sauce over each fillet.