Citron tea, also known as yuja cha, is a popular hot drink in Seoul. It is made from the fruit of the yuzu tree, which is similar to a lemon but has a unique flavor that is both sweet and tangy. Citron tea is often enjoyed during the winter months as it is believed to have warming properties and can help boost the immune system. It is typically served hot and can be enjoyed on its own or with a spoonful of honey for added sweetness.