Add sugar and flour. Stir until well mixed.
Heat pineapple juice and lemon juice together. Cool.
Pour mixtures together, stirring until mixed well.
Pour mixture into heavy sauce pan and cook on medium heat until mixture thickens.
Pour into bowl, cool, cover with clear plastic wrap and chill.
When ready to serve fruit, whip the cream until it forms stiff peaks. Fold the whipped cream into the chilled mixture and serve a generous dollop on each serving of fruit.