1. Preheat oven to 450 F. In nonstick 15 1/2" by 10 1/2" jelly-roll pan (or pan lined with nonstick foil), toss potatoes, 1 tbs oil, 1/2 tsp salt, and 1/4 tsp black pepper until coated; spread in single layer. Roast potatoes, in lower third of oven, 30 to 35 minutes or until golden and tender, turning over once halfway through roasting.
2. Meanwhile, prepare tartar sauce: In small bowl, combine mayonnaise, yogurt, parsley, capers, Dijon, and ground red pepper. Makes 3/4 cup.
3. In cup, combine flour, cornmeal, 1/2 tsp salt, and 1/4 tsp black pepper; use to coat cod.
4. In nonstick 12-inch skillet, heat remaining oil over medium-high heat. Add cod; cook 4 to 6 minutes or until cod turns opaque in center, turning over once. Serve with potatoes, tartar sauce, and lemon.