Examining Q-V characteristics of a Capacitor using LTSpice
Since $$ Q_C = \int i_C dt = \int \frac{v_1}{R_{100}} dt $$
So if you put a perfect integrator on \$R_{100}\$ then you are measuring \$Q_C\$ (times a constant).

Now for example, if you have Spice tabulate \$v_C\$ and \$Q_c\$ at various time and scatter-plot them on a graph, you should see them all fall on a straight line for an ideal C. The slope of the line would be:
$$ \frac{Q_c}{v_c} = C $$