gap> mat := [[1,0,0],[0,0,3],[0,3,0]]*Z(11)^0;
[ [ Z(11)^0, 0*Z(11), 0*Z(11) ], [ 0*Z(11), 0*Z(11), Z(11)^8 ], 
  [ 0*Z(11), Z(11)^8, 0*Z(11) ] ]
gap> phi := PolarityOfProjectiveSpace(mat,GF(11));
<polarity of PG(2, GF(11)),  >
gap> GramMatrix(phi);
[ [ Z(11)^0, 0*Z(11), 0*Z(11) ], [ 0*Z(11), 0*Z(11), Z(11)^8 ], 
  [ 0*Z(11), Z(11)^8, 0*Z(11) ] ]