We were on the Westerdam in October, and Fruit crisp was on the menu every night in the MDR.
And, we asked about Crème Brûlée, as that wasn’t on the menu ( only available in the Pinnacle Grill) and they made it for us the next night in the MDR.
So, yes, certainly ask for anything, and they will try their best to get it for you. 😊