If someone tries to implement the CQRS pattern without repository in DDD, in which layer should it be done? Infrastructure or Application Layer?
If you mean the implementation of the handlers of the queries and commands, it's done in the application layer.
But you need a repository to abstract the technological implementation outside of use cases/interactors (application layer).
The Infrastructure layer is responsible for encapsulating technology. You can find there the implementations of database repositories for storing/retrieving business entities, message brokers to emit messages/events, I/O services to access external resources, framework related code and any other code that represents a replaceable detail for the architecture.