Preheat oven to 300°F (150°C), then grease and flour a 9-inch round cake pan, lining it with parchment paper.

In a medium bowl, whisk together the flour, baking powder, cinnamon, nutmeg, and salt, then set this dry mixture aside.

In a large bowl, use an electric mixer to cream the softened unsalted butter and granulated sugar until they are light and fluffy.

Beat in the eggs one at a time, followed by stirring in the vanilla extract until everything is well combined.

Gradually add the dry ingredient mixture to the wet ingredients, alternating with milk, ensuring you start and end with the dry ingredients and mix until just combined.

Gently fold in the mixed candied fruit, golden raisins, chopped walnuts, and orange zest into the batter.

Pour the prepared batter into the cake pan and bake for 2.5 to 3 hours, or until a wooden skewer inserted into the center comes out clean.

Allow the cake to cool in the pan for 15 minutes before inverting it onto a wire rack to cool completely.