In a saucepan, make the fruit mixture by combining butter, dates, dried fruits, brown sugar, molasses, orange juice, and zest. Simmer the mixture, then let it cool to room temperature.

Preheat the oven to 285°F (140°C) with the fan on. Grease a 6x2 cake pan.

Sift together baking powder, flour, salt, cinnamon, ginger, nutmeg, and allspice.

In a separate bowl, whisk eggs with vegetable oil.

Stir the fruit mixture into the oil and egg mixture.

Gently fold the wet ingredients into the dry ingredients until they are combined.

Add the batter to the prepared pan. Bake for 80 minutes. Cool it in a pan, then on a rack.

For syrup, heat sugar and orange juice until the sugar dissolves. Brush the syrup over the warm cake.

Use foil to wrap the cake and store it for at least 48 hours before serving.