A torrada com manteiga está deliciosa.

Torrada is a feminine noun in Portuguese, so it takes a.

• a torrada = the toast / a piece of toast
• o pão torrado = the toasted bread

In everyday Brazilian Portuguese, torrada is a very natural word for toast. It does not have to be literally a feminine version of an adjective in the learner’s mind; it functions as its own noun.

Portuguese uses articles very often, sometimes more often than English.

So a torrada is natural where English might say:

• the toast
• or sometimes just toast, depending on context

In this sentence, a is the feminine singular definite article, agreeing with torrada.

Because com manteiga here means with butter in a general, descriptive way.

• torrada com manteiga = toast with butter

If you said com a manteiga, it would usually sound like you mean a specific butter already known in the context:

• a torrada com a manteiga da fazenda = the toast with the farm butter

With food ingredients, Portuguese often leaves out the article when speaking generically.

Both ser and estar can be translated as to be, but they are used differently.

Here, está deliciosa is the most natural choice because it describes how the toast is tasting right now or its current state.

• está deliciosa = it tastes delicious / it is delicious right now

If you said é deliciosa, it would sound more like a general characteristic:

• Torrada com manteiga é deliciosa. = Toast with butter is delicious.

So:

• está = specific situation, current experience
• é = general truth, permanent or defining quality

Because adjectives usually agree in gender and number with the noun they describe.

The noun is:

• a torrada = feminine singular

So the adjective must also be feminine singular:

• deliciosa

Compare:

• o pão está delicioso
• a torrada está deliciosa
• as torradas estão deliciosas

It is a prepositional phrase modifying torrada.

• com = with
• manteiga = butter

So a torrada com manteiga means the toast with butter or the buttered toast, depending on context.

It tells you what kind of toast you are talking about.

Yes, but it is less common in everyday speech for this exact idea.

• a torrada com manteiga = very natural, straightforward
• a torrada amanteigada = buttered toast, but a bit more descriptive or formal-sounding

In normal conversation, Brazilians are very likely to say com manteiga.

Because deliciosa is not directly modifying the noun inside the noun phrase; it is part of the predicate with está.

Structure:

• A torrada com manteiga = subject
• está deliciosa = predicate

So the sentence literally works like:

• The toast with butter is delicious

If you wanted an adjective directly attached to the noun, it would look more like:

• a deliciosa torrada
  But that is much less neutral and sounds literary or emphatic.

Usually, that sounds less natural in standard Portuguese.

The version with the article is much more natural:

• A torrada com manteiga está deliciosa.

Without the article, it may sound like:

• a headline
• a recipe label
• very telegraphic speech

Portuguese generally likes articles in ordinary sentences.

You would make the noun, verb, article, and adjective plural:

• As torradas com manteiga estão deliciosas.

Breakdown:

• a → as
• torrada → torradas
• está → estão
• deliciosa → deliciosas

Manteiga stays singular here because it is still butter as a mass noun.

Yes. Depending on context, torrada can refer to:

• toast in general
• a slice/piece of toast
• in some contexts, a crunchy toast or toast cracker-like item

In this sentence, learners can understand it simply as toast.

Both are possible, but they feel slightly different.

• deliciosa = delicious
• gostosa = tasty / yummy / delicious

For food, both are common in Brazilian Portuguese.
Deliciosa is a little more neutral and easy for learners.
Gostosa is extremely common in Brazil, but it can also describe a person in an informal way, so learners should be aware of that extra meaning.

A rough pronunciation guide for an English speaker is:

• A ≈ ah
• torrada ≈ toh-HAH-dah
• com ≈ kohng / kohm depending on accent
• manteiga ≈ mahn-TAY-gah
• está ≈ es-TAH
• deliciosa ≈ deh-lee-see-OH-zah

A few helpful notes:

• The rr in torrada is not like the English r. In Brazil, it is usually a throaty h-like sound.
• The stressed syllables are:
  • torRAda
  • manTEIga
  • esTÁ
  • deliciOsa

A very natural version is:

• Torrada com manteiga é deliciosa.

Here, é works better because you are talking about a general truth, not a specific piece of toast in front of you.

So compare:

• A torrada com manteiga está deliciosa. = this toast with butter is delicious
• Torrada com manteiga é deliciosa. = toast with butter is delicious in general