Peel, core, and halve the pears.
Combine the acesulfame-K or sugar and water in a saucepan and bring to a boil.
Reduce the heat to low and add the vanilla bean and pear halves.
Simmer for 5 minutes or so, until the pears are fork-tender.
In a small bowl, gently toss the raspberries and jelly.
Put two pear halves on each serving plate.
Mound the raspberries on top of the pears.