Pre-heat the oven to 190?C/375?C/gas mark 4 Drain the pineapple rings. Spread about a third of the low fat spread over the sides and base of a 20cm (8 inch) cake tin. Lay the pineapple rings out over the base of the tin as tightly as possible, but not overlapping. Sprinkle generously with caster sugar. Cream the remaining spread and sugar together. Add the juice from the pineapple, then gradually add the flour, vanilla, eggs and enough milk to form a thick custard consistency. Make sure there are no lumps before you pour it all over the pineapple rings. Shake gently to settle everything, then place in the oven for about 30 minutes or until golden brown and set. Turn out and serve warm with vanilla or coconut ice cream.