We consider a rotating turbulent fluid with low Rossby number. It is known that inverse energy cascade is inspired in three-dimensional turbulent flow due to the fast rotation. Under certain condition, the inverse cascade results in establishing coherent columnar vortices. We discuss the way how kinetic energy is transferred from small-scale eddies to the large-scale vortex. As a result, the Reynolds stress tensor is found and the structure of the vortex is determined.