It would be GatavYAT if the stress was on the last syllable. Since in this case the middle syllable is stressed, it's technically "GaTOVyet," the last syllable of which is often incredibly soft and sounds like an "i" to non-Russian ears
As a Russian (teacher of this account)I hear wrong pronunciation here. It should be "Gatoviat" as in они готовят where я is pronounced as "ya" or "ia" but not as "i".
The pronunciation is absolutely correct, assuming you and I are hearing the same voice. In most Russian words, the unstressed syllables have vowels that undergo reduction. In this case, the Я becomes an /ɐ/ or /ə/sound following a palatalized "вь" sound.
Is there something wrong with the translation: "Yes, they are currently cooking."?