Reduce apple juice with the lemon juice in a sauce pan until it reaches the consistency of syrup. Add frozen raspberries and rum and continue cooking until the raspberries are melted and the alcohol in the rum evaporates. In a strainer, separate the solid ingredients from the liquid ingredients and discard the solid ingredients. In a cocktail shaker take the strained raspberry mixture, the vinegar and oil and shake until well mixed. Finally add the poppy seeds to the mixture and serve over a bed of fresh spinach and feta cheese.