Learn Portuguese (Portugal): Foi o gestor que contratou o especialista ontem. - It was the manager who hired the specialist yesterday.

In Portuguese, the relative pronoun que is used for both things ('that' or 'which') and people ('who'). While quem does mean 'who', it is mostly used after prepositions (like com quem - with whom) or when there is no specific noun right before it. Since que directly refers back to the specific noun o gestor, it is the normal and correct choice here.

Could I just say O gestor contratou o especialista ontem? What does foi ... que add?

Yes, you could! Saying O gestor contratou... simply means 'The manager hired...'. Adding foi (it was) and que (who/that) creates an emphatic structure. It highlights exactly who did the hiring: 'It was the manager who hired the specialist yesterday' (emphasizing that it wasn't the director or the HR department).

Why use the past tense foi (it was) rather than era?

Both foi and era mean 'was', but foi (the simple past or preterite) is used here because it frames a specific, completed, one-time action in the past: the hiring that happened ontem (yesterday). You use era for ongoing background descriptions, but a specific hiring event yesterday is a single completed action.

Especialista ends in '-a', so why is it paired with the masculine article o?