  We present numerical solutions to Einstein's equations describing large
spherical cosmic voids constituted by two components; dark matter and baryons,
with a non-vanishing initial relative velocity, in an asymptotically
homogeneous background compatible with the $\Lambda$CDM concordance model. We
compute numerically the evolution of such configurations in the dark matter
frame, with a hypothetical homogeneous distribution of baryons, but respecting
the values dictated by the concordance model for the average baryon-to-dark
matter density ratio. We reproduce the well known formation of overdensities at
the edge of the void, and recover the Lemaitre-Tolman-Bondi solutions in the
comoving limit of our simulations. We compute the average growth factor of
matter fluctuations, and find that it departs significantly from the linear
perturbative prescription even in the comoving case, where the non-linearity of
inhomogeneities has an impact.
