There is no lactose in tomatoes! Also, lactose-free butter is prepared from lactose-free cream, which could have been used to prepare your dessert. As for the lactase pill, you can/should take it along with your meal and not before it. Thus, even without a description, it is never too late once you see that you've been served dairy products. Finally, if you don't like margarine, simply don't eat it. One meal without extra fat has never harmed anybody.

Yes, I know, I sound like a general practitioner teaching his patient what to eat. Even 50 years after graduating from Med School, I can't forget my sins of the youth...