To make stuffing:
In a pan, melt margarine until bubbling. Add onion and cook until soft. Stir in savory, mixing well. Add crumbs and stir to combine. Set aside.
Cut a cavity in the side of each cod portion; insert ¼ of the stuffing into each piece. Season with salt and pepper. Lay 2 slices of lemon on top of each, saving a few slices for garnish.
Transfer to a lightly greased baking sheet and bake in a 400ºF (200ºC) oven for 15 minutes.
Serve, garnished with extra lemon slices.
Makes 4 servings.