In a mixing bowl, mix together flour, sugar, baking powder, baking soda, and salt.
In another small bowl, beat eggs lightly with a whisk or fork, then stir in melted butter, orange peel, and orange juice.
Add the wet mixture to the flour mix, and stir with a spoon until the batter is just mixed, then fold in the cranberries and walnuts (batter will be stiff).
Pour the batter into the loaf pan and bake in the preheated oven for 55-60 minutes or until a toothpick inserted in the middle comes out fairly clean (a crumb or two can stick to it but you don't want wet batter).
Cool in the pan on a wire rack for 10 minutes, then remove from the pan and finish cooling on the wire rack.