Apesar de o bolo ser doce, o gosto do limão destaca-se.

Apesar de is a concessive expression. It introduces a contrast: one thing is true, but another point is still important.

Here it works like:

• despite
• in spite of
• sometimes although

So the structure is basically:

Apesar de + clause / noun phrase, ...

In this sentence, it sets up the contrast between the cake being sweet and the lemon taste still standing out.

Normally, de + o = do in Portuguese.

However, in careful standard writing, many speakers and grammars prefer not to contract them when o bolo is the subject of an infinitive clause:

• apesar de o bolo ser doce

This helps show the structure more clearly:

• o bolo = subject
• ser doce = infinitive clause

You may still hear or see apesar do bolo ser doce, especially in less formal use, but apesar de o bolo ser doce is a very standard and safe choice.

Because Portuguese is using an infinitive clause here, not a normal finite clause.

So instead of saying something like:

• although the cake is sweet

Portuguese often says:

• despite the cake being sweet

That is why you get:

• o bolo ser doce

and not:

• o bolo é doce

A useful point: this can become a personal infinitive, which shows agreement in some forms. For example:

• Apesar de os bolos serem doces...

Here serem shows plural agreement.

This is the classic ser vs estar distinction.

• ser doce = to be sweet as a characteristic or defining quality
• estar doce = to be sweet as a temporary state or current result

In this sentence, the cake’s sweetness is treated as a general property, so ser sounds natural.

If you were commenting on how it tastes right now, especially in a more immediate or subjective way, estar could also appear in other contexts, for example:

• O bolo está muito doce.

That sounds more like The cake tastes very sweet / is too sweet right now.

Here it is a noun:

• o gosto = the taste

That is easy to miss because gosto can also be the 1st person singular of the verb gostar:

• Eu gosto de limão. = I like lemon.

In your sentence, the article o shows that it is a noun:

• o gosto do limão = the taste of lemon

Yes, gosto and sabor can both work here.

Very roughly:

• gosto = taste
• sabor = flavor

In real use, they overlap a lot.

In this sentence:

• o gosto do limão destaca-se
• o sabor do limão destaca-se

Both are natural.

A small nuance:

• gosto can feel a bit more everyday
• sabor can feel a bit more specifically about flavor

But the difference is not huge here.

Do is simply the contraction of:

• de + o = do

So:

• o gosto do limão = the taste of the lemon / of lemon

Portuguese often uses the definite article in places where English would not.

Also, de limão is especially common when the phrase is more classificatory, for example:

• bolo de limão = lemon cake
• gelado de limão = lemon ice cream

But in o gosto do limão, the idea is the taste/flavor associated with lemon, so do limão is very natural.

Destacar-se means to stand out, to be noticeable, or to be prominent.

So o gosto do limão destaca-se means that the lemon taste is the element that becomes noticeable or prominent.

About the se:

• it is part of the verb destacar-se
• it is not really a literal reflexive it highlights itself
• it helps form the pronominal verb meaning to stand out

In European Portuguese, clitic pronouns often come after the verb in affirmative main clauses:

• destaca-se

This is called enclisis.

You can compare:

• Destaca-se.
• Não se destaca.

After não, the pronoun moves before the verb.

Yes. A very natural alternative is:

• Embora o bolo seja doce, o gosto do limão destaca-se.

This version uses:

• embora = although
• seja = subjunctive of ser

So the difference is mainly grammatical:

• apesar de o bolo ser doce → infinitive structure
• embora o bolo seja doce → finite clause with subjunctive

Both are good Portuguese. The original sentence is just using the infinitive pattern.

Because the sentence begins with a fronted concessive clause:

• Apesar de o bolo ser doce, ...

That opening part sets the contrast, and the comma separates it from the main clause:

• o gosto do limão destaca-se

This is the normal punctuation in Portuguese, just as in English you would often write:

• Although the cake is sweet, the lemon taste stands out.