The real(M) function computes the element-wise real part of M.  The result, R, is formed as R[i,j] = real(M[i,j]).

$\mathrm{with}\left(\mathrm{MTM}\right)\:$

$M≔\mathrm{Matrix}\left(2\,3\,'\mathrm{fill}'=-3+\mathrm{I}\right)\:$

$\mathrm{real}\left(M\right)$

$\left[\begin{array}{ccc}\mathrm{-3}& \mathrm{-3}& \mathrm{-3}\\ \mathrm{-3}& \mathrm{-3}& \mathrm{-3}\end{array}\right]$