It's actually the simple present passive voice in English---formed by the present tense of be and the past participle of the verb. https://www.grammarbank.com/simple-present-passive.html
Past tense would be "How was xxx said?"
In this case it's not about how you, personally, say something, but rather about how it's, generally, said. The English sentence uses the general, impersonal "you" that is often used in general advices, like "You should brush your teeth twice a day". No you, personally, but society at large.
Those generalisations are usually expressed with the 3rd person reflexive form: "¿Cómo se dice ...?" - "How do you say ...?", "How is ... said?"
It's okay, but not a formal sentence, since it lacks a conjugated verb. This "se dice" construction is in the Spanish passive voice, so you could go for that in English: "How is 'cat' said in Italian?"
Or you could go for an impersonal sentence, using the subject "one" in English, or the impersonal "you": "How does one say 'cat' in Italian?" "How do you say 'cat' in Italian?" Lots of options.