Heat butter, sugar, fruit, spice, baking soda and syrup into a saucepan. Heat over a medium heat till butter melts, stirring often. Allow to cool fully at least an hour. Heat oven to 125 C. Grease 2 x deep 20cm tins, and triple line with baking paper, making sure it extends up the sides beyond the tin. Beat eggs and stir through cooled fruit mix. Sift dry ingredients, fold into fruit mix with orange zest.
Spoon into tins, bake for 3-3 ½ hours or until tested with a skewer and it comes out clean. Decorate once cool.
Store in an air tight container, dry place. Will keep for at least a year, and stays deliciously moist.