Normalized cross-correlation in frequency domain
I was thinking on the math behind it and concluded that calculating the NCC in the frequency domain is basically the same process as in the time domain:

$F[k]$ is the (discrete) Fourier transform of my sample, $G[k]$ is the gaussian curve in the frequency domain. The cross-correlation is
$$CC = \sum^{L-1}_{k=0}F[k]{\cdot}G[k]$$
Then, to get the normalized cross-correlation we first normalize the vectors $F$ and $G$, as would be done to any vector:
$$\hat{v} = \frac{v}{|v|} = \frac{v}{\sqrt{\sum^{L-1}_{k=0}v^2[k]}}$$
Thus, the normalized cross-correlation should be the dot-product of the normalized vectors $\hat{F}$ and $\hat{G}$:
$$NCC = \frac{\sum^{L-1}_{k=0}F[k]{\cdot}G[k]}{\sqrt{\sum^{L-1}_{k=0}F^2[k]\cdot\sum^{L-1}_{k=0}G^2[k]}}$$