ABSTRACT We have developed a new method for spectral analysis of binaries. Our method successfully identifies double-lined spectroscopic binary (SB2) candidates from high-resolution Gaia-ESO spectra. Compared to the commonly used cross-correlation function analysis, it works for binaries with rapidly rotating components. We test our method on synthetic and observational spectra of BAFG stars with vsin i from 1 to $330~\, {\rm km}\, {\rm s}^{-1}$ in the open cluster M11. We confirm five previously detected SB2 candidates and find 19 new ones. For three SB2 candidates, we find circular orbits and obtain dynamical mass ratios.