Wash sweet potatoes, apples and fresh cranberries. Discard and compost any mushy cranberries.
Cut the peeled sweet potatoes into medallion slices, approximately ¼” thick. Cut the apples into slices of a similar thickness, or just a tad thinner - about ⅛ to ¼” thick.
Add a single layer of sweet potato medallions to the bottom of your lightly greased baking dish, filling as much empty space between the pieces as possible. Next, do the same with a layer of apple slices.
Next, add about 2 heaping cups of fresh cranberries and 3/4 cup walnuts on top of the sweet potato and apple layer - distributed evenly across the top.
If you’re using a stick of butter, cut off 3 tablespoons and then divvy it into about 8 to 9 even tabs to spread evenly over the dish. Or, follow a similar process with your butter replacement of choice.
Sprinkle over a few shakes or pinches of salt across the entire surface - about an ⅛ of a teaspoon. Now do the same with a pinch of both allspice and nutmeg, but go slightly lighter than the salt - less than ⅛ a teaspoon each. Finally, evenly sprinkle 1/2 teaspoon of cinnamon and 2.5 tablespoons of light brown sugar over the whole dish.
Preheat the oven to 400F.
Repeat the steps above to create another tightly-packed layer of sweet potatoes, apples, cranberries, walnuts, butter, and seasonings.
Cover the dish with tin foil or an oven-safe lid, and bake at 400F for one hour total (the first 50 minutes covered, and uncovered during the last 10 minutes to lightly toast the walnuts)
Enjoy! It is best served warm, but is pretty dang good cold too - like a pie. It gets even better with time, and makes for excellent leftovers! Store the leftovers in the refrigerator, and enjoy within one week of baking.