That's a great question. Kotlin can be used with any of the major Java frameworks, so there's Spring is still a popular choice. Spring 5.0 introduced extensions that allow for more idiomatic Kotlin code and is proving popular.
Once of the most interesting innovations to come from the Kotlin community is the Ktor framework. This is an asynchronous framework that has a number of similarities with Node. You can find an introductory tutorial to Ktor here: