Parasitic coil capacitance refers to parallel capacitance, I presume. Thus you are looking for the parallel resonance of the unloaded coil. The best approach for unloaded resonance measurement is a weakly coupled grid dip meter or an equivalent setup.
The fact that your measurement shows two resonances makes clear that your setup isn't a simple LC parallel circuit but some kind of LCC or LLC circuit. And most likely parasitic parameters of the measurement setup are falsifying the original resonance frequency.