Learn Hardcore Portuguese (Portugal): O pão está cortado.

In Portuguese, estar expresses a temporary state or condition, while ser (é) describes inherent qualities or permanent facts. Since the sentence refers to the state of the bread (it’s in a cut condition right now), we use está.

Is O pão está cortado a passive‐voice sentence?

Not in the same way English “The bread is cut” can be a true passive. In Portuguese this is a stative or resultative construction:

está
- past participle = describes the resulting state.
  You could call it a “pseudo‐passive,” but it doesn’t focus on who did the cutting—only on the fact that the bread is now cut.

Is cortado acting as an adjective or a past participle here?

It’s originally the past participle of cortar, but in this sentence it functions like an adjective describing the state of the bread. That’s why it agrees in gender and number when you change it to plural (see next question).

How would I say “the breads are cut”?