🚀 go-pugleaf

I would appreciate any suggestions on practical methods
for extracting spectral information from a noisy signal.
In particular I need to measure the amplitude of
one sinusoidal component (whose frequency is known in
advance) where the amplitude of the component is
close to the noise level. My first thought was to use
an FFT to estimate the power spectrum and then try to
identify the peak, but I feel sure that there must be
a better way. Maybe digital filtering or some other
means of power spectrum estimation (such as the Maximum
Entropy Method) ? Or perhaps I should be doing something
in the time domain, such as autocorrelation + averaging ?

Suggestions, ideas, examples, source code, all welcome.