No. You can pour all the ingredients into a saucepan and cook it over low heat until the mixture thickens the back of a wooden spoon. Having said that, fruit curd made with acidic fruits such as lemons, oranges, pineapples, or passion fruit tend to split easily when a little overheating due to the acid. The double boiler method is a sure way of preventing that. Unless of course, you cook that over very high heat!