Exegesis:

Dauid oun kurion auton kalei ‘so David calls him Lord.’ oun is inferential and means here, ‘as scripture shows,’ ‘as we have seen.’

pōs autou huios estin ‘how (is it possible that) he is his son?’

Translation:

Calls him Lord, or, ‘causes/says-(him-)to-be-lord’ (Toraja-Sa’dan, using a causative-declarative verbal derivation of ‘lord’). Him, or to avoid ambiguity, ‘the Messiah.’

His son, or, ‘David’s son,’ again for the sake of clarity.

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.