Preheat oven to 400ºF (200ºC).
In large deep bowl in refrigerator, soak salt cod in cold water for 24 hours, changing water 4 times. Taste salt cod; if still too salty, continue changing water and soaking for up to 8 hours longer. Drain and rinse; cut into 2-inch (5 cm) chunks. Set aside.
In large skillet, heat 2 tablespoons (25 mL) of the oil over medium-high heat; cook onions, garlic and hot pepper flakes until softened and golden, about 15 minutes.
Add wine; cook, stirring, for 1 minute. Add tomatoes, red peppers, coriander and pepper; bring to boil. Reduce heat and simmer, stirring occasionally, until sauce is thick enough to mound on spoon, about 30 minutes. (Make-ahead: Let cool for 30 minutes; refrigerate until cold. Refrigerate in airtight container for up to 1 day.)
Peel and cut potatoes into 1/8-inch (3 mm) thick slices; toss with remaining oil. In greased 10-x 14-x 2 3/4-inch (25 x 35 x 7 cm) roasting pan, layer one-third of the potatoes; sprinkle with half each of the reserved cod then sauce. Repeat layers once. Top with remaining potatoes.
Bake in oven until potatoes are browned, about 2 hours. (Make-ahead: Let cool for 30 minutes; refrigerate until cold. Cover with plastic wrap and refrigerate for up to 1 day. Replace plastic wrap with foil; reheat in 350ºF (180ºC) oven until hot, about 1 hour.) Let stand for 10 minutes.