In a large bowl, combine the diced pears, sugar, and cardamom. Make a long slit in the vanilla bean, and, using the tip of your knife, remove the inside of the vanilla bean, and add it to the bowl. Add the entire contents to the melted butter on your stovetop. I usually throw in entire vanilla pod into the pan for good measure. Stir well so the pears are coated in the butter and sugar.