To make the fish
and vegetables: Preheat oven to 425 degrees F.
Prick each potato once with a fork, then rub potatoes
with 1/2 tablespoon oil. Roast
on a baking sheet in middle of oven until just tender, about 25 minutes. Cool to room temperature and cut crosswise into 1/4-inch-thick slices. Leave oven on.
Heat remaining 1 1/2 tablespoons oil in a 12-inch heavy skillet over moderately high heat until hot but not smoking, then saute bell peppers, stirring, until just tender, 6 to 8 minutes.
Spread potato slices evenly in an oiled 13 by 9 by 2-inch glass baking dish
and season with salt and pepper. Top with peppers, then tomatoes
and fish, seasoning each layer with salt and pepper. Sprinkle fish with lemon juice.
To make the Charmoula Sauce: Puree all sauce ingredients except oil in a food processor
. With motor running, add oil in a slow stream.
Pour sauce evenly over fish and bake in middle of oven until fish is just cooked through, 25 to 30 minutes.