Peel, then slice sweet potatoes crosswise into 1-inch-thick slices.
Arrange potato slices and the orange slices in alternate layers in a 1 1/2 -quart casserole.
Combine the cornstarch, brown sugar, and salt; add orange peel and butter.
Pour in orange juice, and stirring, cook over low heat until smooth and thickened.
Pour sauce over the potato and orange layers; top with pecan halves.
Bake in a moderate oven (350°) for 30 minutes, or until heated through and glazed.