Epitaxial 3C-SiC layers were obtained on on-axis, 3x3 reconstructed, Si-terminated faces of 6H single crystals, grown by the modified Lely method. The epilayers were grown through repeated steps of two silicon monolayer deposition by MBE, followed by a carbonization reaction using C2H4 gas, and annealing. With the help of in situ (LEED, X-ray photoelectron spectroscopy and diffraction) and ex situ controls (cross-section transmission electron microscopy (TEM)), the deposited layer was identified to be an epitaxial single 3C-SiC phase. The epitaxy relationship corresponds to a (111) plane of the cubic structure parallel to the (0001) 6H-SiC plane with a [110] direction of 3C-SiC parallel to a [1100] direction of the hexagonal structure. As this implies two orientation possibilities of the 3C-SiC structure with respect to the substrate, twinned domains are formed. When examined by TEM, superimposed twinned domains oriented along <110> zone axes give rise to moire effects, which can be confused with a 9R polytype structure. We show how the 9R assumption can be ruled out from a careful analysis of both high resolution images and corresponding electron diffraction.