Eu misturo a massa do bolo na tigela.

Because misturo is the conjugated verb: it means I mix.

• misturar = to mix (the infinitive)
• misturo = I mix

In Portuguese, you usually need a conjugated verb in a normal sentence. For misturar, the eu form in the present tense is misturo.

Yes. Misturo is the present tense.

In Portuguese, the simple present can often cover both:

• I mix
• I am mixing

So Eu misturo a massa do bolo na tigela can work in a general sense or in a current-action sense, depending on context.

In European Portuguese, if you want to make the ongoing action especially clear, you often use:

• Estou a misturar a massa do bolo na tigela. = I am mixing the cake batter in the bowl.

That estar a + infinitive pattern is very common in Portugal.

You can usually leave out eu.

Portuguese often drops subject pronouns because the verb ending already shows who the subject is:

• misturo clearly means I mix

So both are correct:

• Eu misturo a massa do bolo na tigela.
• Misturo a massa do bolo na tigela.

Including eu can add emphasis, contrast, or clarity.

For example:

• Eu misturo a massa, tu preparas a forma.
  I mix the batter, you prepare the tin.

A is the definite article meaning the.

• a massa = the batter / the dough

It is a because massa is a feminine singular noun.

Compare:

• a tigela = the bowl
• o bolo = the cake

Portuguese uses definite articles more often than English does, so seeing a and o in sentences like this is very normal.

Not always. Massa can mean different things depending on context.

Common meanings include:

• dough
• batter
• paste
• mass
• sometimes even pasta in some contexts, though that depends a lot on region and usage

In a massa do bolo, it means cake batter.

So here it does not mean a finished cake; it means the mixture before baking.

Because de + o contracts to do in Portuguese.

So:

• de o bolo → do bolo

This is a very common contraction.

Other common ones:

• de + a = da
• de + os = dos
• de + as = das

So:

• a massa do bolo = the cake batter
• literally, something like the batter of the cake

Do bolo specifies which batter it is.

• a massa = the batter / the dough
• a massa do bolo = the cake batter

It works like a noun phrase that narrows the meaning:

• massa do pão = bread dough
• massa da pizza = pizza dough

So do bolo tells you that this massa belongs to or is for a cake.

Because na is a contraction of em + a.

• em = in / on / at
• a = the
• em a → na

So:

• na tigela = in the bowl

This kind of contraction is extremely common in Portuguese.

Other examples:

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

So:

• no forno = in the oven
• na cozinha = in the kitchen

Both are possible, but they mean slightly different things.

• na tigela = in the bowl
  This usually refers to a specific bowl, one already known in the situation.
• numa tigela = in a bowl
  This sounds less specific.

So:

• Eu misturo a massa do bolo na tigela.
  suggests a particular bowl
• Eu misturo a massa do bolo numa tigela.
  means in a bowl, not necessarily a specific one

In Portuguese:

• em + uma = numa

It means inside the bowl / in the bowl, not with the bowl as an instrument.

So the bowl is the location of the mixing.

If you wanted to express the idea of using something as a tool, Portuguese would normally use a different structure, often with com:

• Misturo com uma colher. = I mix with a spoon.

But here:

• na tigela = where the action happens

The given word order is natural:

• Eu misturo a massa do bolo na tigela.

You can sometimes move parts around, but not every version sounds equally natural.

For example:

• Na tigela, eu misturo a massa do bolo.
  This is fine if you want to emphasize where the action happens.
• Eu, na tigela, misturo a massa do bolo.
  Possible, but less neutral.
• Eu misturo na tigela a massa do bolo.
  Understandable, but usually less natural than the original neutral order.

A good default pattern is:

• subject + verb + object + place

That is exactly what this sentence uses.

Because grammatical gender in Portuguese belongs to each noun individually.

So:

• o bolo = masculine
• a massa = feminine
• a tigela = feminine

This affects the article:

• o for masculine singular
• a for feminine singular

The gender does not have to match across the whole sentence. Each noun keeps its own gender.

In European Portuguese, misturo is typically pronounced roughly like:

• mish-TOO-roo

A bit more precisely:

• the s before t sounds like sh
• the r is usually a tapped r
• unstressed vowels are often reduced in European Portuguese

So learners often notice that European Portuguese sounds more compressed than Brazilian Portuguese.

A rough learner-friendly pronunciation for the whole sentence could be:

• Eu mish-TOO-ro a MAH-suh du BOH-lu na ti-JEH-luh

But the exact sound will depend on accent and speed.

For the bowl, em is the normal choice because you are saying where the mixing happens.

So:

• na tigela = in the bowl

Other prepositions would change the meaning:

• com uma colher = with a spoon
• para o bolo = for the cake
• de chocolate = of chocolate / chocolate-flavoured, depending on context

So in this sentence, em is the right idea, and because of contraction it becomes na.

Yes, it sounds natural and correct in European Portuguese.

A speaker in Portugal might also say:

• Misturo a massa do bolo numa tigela.
• Estou a misturar a massa do bolo na tigela.

But the original sentence is perfectly normal as a simple present statement.