Enquanto o bolo estava no forno, a cozinha começou a cheirar muito bem.

Enquanto means while.

It introduces an action that was in progress in the background:

• Enquanto o bolo estava no forno... = While the cake was in the oven...

In sentences like this, enquanto often sets the scene for another event that happened during that time.

Estava is the imperfect tense of estar. It is used because the cake being in the oven is a continuous background situation, not a single completed event.

So:

• o bolo estava no forno = the cake was in the oven / was being in the oven as an ongoing situation

If you used esteve, it would sound more like a completed, bounded event, which is not the natural focus here.

This is a very common pattern:

• background action/state → imperfect
• event that begins or happens during that background → often perfect

That is exactly what happens in this sentence.

Because Portuguese normally contracts em + o into no.

So:

• em + o = no
• em + a = na
• em + os = nos
• em + as = nas

Therefore:

• no forno = in the oven

This contraction is required in normal Portuguese.

It means started to smell.

This uses a very common structure:

• começar a + infinitive = to start/begin to + verb

So:

• começou a cheirar = started to smell

Other examples:

• começou a chover = it started to rain
• comecei a estudar = I started to study

Because the sentence is talking about the kitchen beginning to smell good, not directly about the cake itself.

So the idea is:

• the cake is in the oven
• as a result, the kitchen starts smelling nice

This is natural in both Portuguese and English:

• The kitchen started to smell really good

If you made o bolo the subject, the meaning would shift more toward the cake itself smelled good.

It can mean both, depending on the subject and context.

1. To give off a smell / to smell

• A cozinha cheira bem. = The kitchen smells good.
• Isto cheira a café. = This smells like coffee.

2. To sniff / to smell something intentionally

• O cão cheirou a comida. = The dog sniffed the food.

In your sentence, a cozinha começou a cheirar muito bem, it clearly means to smell in the sense of giving off a pleasant smell.

Because bem is the adverb normally used with the verb cheirar in this kind of sentence.

• cheirar bem = to smell good
• cheirar mal = to smell bad

So:

• a cozinha começou a cheirar muito bem = the kitchen started to smell really good

By contrast, bom is an adjective, so it usually describes a noun:

• um cheiro muito bom = a very good smell

So the difference is:

• cheira muito bem → adverb with the verb
• tem um cheiro muito bom → adjective with the noun cheiro

No, that would not be standard.

With cheirar used this way, Portuguese normally uses bem, not bom:

• correct: cheira bem
• not standard: cheira bom

If you want to use bom, you need a noun:

• A cozinha começou a ter um cheiro muito bom.
• Havia um cheiro muito bom na cozinha.

But the original sentence is more natural.

Because the sentence begins with a subordinate clause:

• Enquanto o bolo estava no forno, ...

After that introductory clause, a comma is normally used before the main clause:

• ..., a cozinha começou a cheirar muito bem.

This is standard punctuation and makes the sentence easier to read.

Portuguese uses definite articles more often than English does.

So where English might say:

• While cake was in the oven... — though in natural English we would usually still say the cake, the oven

Portuguese very naturally says:

• o bolo
• o forno
• a cozinha

This is completely normal. Learners often notice that Portuguese likes articles in places where English may omit them.

Sometimes, yes, depending on the English sentence.

Here, the best translation is usually while:

• Enquanto o bolo estava no forno... = While the cake was in the oven...

In some contexts, English as can overlap with while, but while is the safest and clearest match for enquanto when two actions or situations happen during the same time period.

Yes. It is natural and correct in European Portuguese.

A European Portuguese speaker might also say similar things like:

• Enquanto o bolo estava no forno, começou a sentir-se um cheiro muito bom na cozinha.
• Enquanto o bolo estava no forno, a cozinha ficou a cheirar muito bem.

But your original sentence is fully natural and idiomatic.