meanwhile, make the compote
In a medium saucepan, let the rhubarb, sugar, vanilla bean and salt stand until slightly juicy, 20 minutes. Add the zest and ginger and cook over moderate heat, stirring occasionally, until the rhubarb is tender, about 15 minutes. Add the St.-Germain and raspberries and cook until slightly thickened, about 5 minutes. Transfer the compote to a bowl and let cool. Discard the vanilla bean.