Pineapple fruit cake

This recipe is quick, easy and has not failed me in 30 years!

1 cup sugar
1 can crushed pineapple (440gm)
500gm mixed fruit (I buy the ready mixed fruit but sometimes throw in some extra cherries, seeded raisins or chopped figs. I also add chopped nuts sometimes - especially at Christmas)
1-2 tsp. mixed spice
1 tsp. bicarb. soda
125gm butter
1 cup self raising flour
1 cup plain flour
2 large eggs - well beaten

Put the sugar, pineapple (including the syrup), fruit, spice, bicarb, and butter in a saucepan and bring to the boil. Boil for a maximum of 3 minutes. Leave until cold. Sift the flours and stir in the cold fruit mixture and the beaten eggs.
Cook in a large square cake tin lined with aluminium foil for 1 hour at a moderate oven and then reduce the heat to a moderately slow oven (350° down to 300°F, or 175° down to 150°C) until it is cooked. I cover the cake loosely with foil after about an hour to stop the top from burning.