  In this paper we give a new general method to describe all Kaehler scalar
flat metrics on $U(n)$-invariant domains of C^n in a way to be able to detect
easily whether it can be completed to larger domains and which kind of ends
they can have. This new approach makes possible to decide whether the
corresponding metrics contain a minimal sphere among the standard euclidean
ones. We will show also how to check the stability (i.e. minimizing volume up
to second order) of such submanifolds. We apply the present analysis to a
comparison between Penrose Inequality, which requires the presence of a stable
minimal hypersurface, and Hein-LeBrun's, which requires the ambient space to be
Kaehler and predicts the existence of a special divisor, and we will show that
Penrose Inequality does indeed hold in any dimension for this class of
manifolds, and that the two inequalities are indeed incomparable in that for
these manifolds a stable minimal surface and a divisor never coexist.
