Why there is no supply on monopoly markets?
The argument is that the monopolist's decision is based on the demand curve (in effect matching marginal total revenue to marginal cost) so is not independent of the demand curve, and in that sense there is not a corresponding supply curve with price and quantity in equilibrium where the two curves cross; the monopolist equilibrium point is likely to be at a lower quantity and higher price.
The conventional demand curve illustrates the price against quantity.  If instead the demand curve illustrated marginal total spending against quantity, then where it crossed the supplier's marginal cost curve would give the monopolist equilibrium quantity (though not the equilibrium price), and in that sense the monopolist's marginal cost curve could the be seen as the supply curve.