a = 5;
b = .1;
f = (1 + Exp[(k - a)]);
B = f*(1/(z - (q^2 + k*q*x) + I*b) +
    1/(z - (q^2 - k*q*x) + I*b));
ListContourPlot[
NIntegrate[Re[B], {x, -1, 1}, {k, -a, a}], {z, 0, 5,
 1}, {q, 0, 5, 1}]