  We introduce a new estimator of the CMB lensing power spectrum, together with
its likelihood, based on iterative lensing reconstruction. Despite the
increased complexity of the lensing maps, this estimator shares similarities
with the standard quadratic estimator. Most importantly, it is unbiased towards
the assumptions done on the noise and cosmology for the lensing reconstruction.
This new spectrum estimator can double the constraints on the lensing amplitude
compared to the quadratic estimator, while keeping numerical cost under control
and being robust to errors.
