Asa la mazorca primero.

Asa is the affirmative informal command (the tú command) of the verb asar, which means to roast, to grill, or sometimes to toast, depending on context.

So:

• asar = to roast / to grill
• asa = roast! / grill! (said to one person informally)

In Spain, this is the normal way to tell one person you know well to do something.

Because affirmative tú commands in Spanish usually use the same form as the él/ella/usted form of the present tense.

For asar:

• tú asas = you roast
• él/ella/usted asa = he/she roasts / you roast
• command to tú: asa

So although tú normally goes with asas, the command form is asa.

Spanish often leaves out subject pronouns because the verb form already tells you who the subject is.

So instead of saying:

• Tú asa la mazorca primero

Spanish normally just says:

• Asa la mazorca primero

This sounds more natural. You could add tú for emphasis, but normally you would not.

Mazorca usually means an ear of corn or the corn cob/corn on the cob.

Depending on context, English might translate it slightly differently:

• ear of corn
• corn on the cob
• corn cob

If the meaning has already been given to the learner, the main thing to know is that mazorca refers to the whole cob, not just loose kernels.

Spanish uses the definite article la more often than English uses the.

So even if English might say something like Roast corn first or Roast the corn first, Spanish naturally says:

• Asa la mazorca primero

The article is very normal here because it refers to the item being cooked.

Primero means first, and its position is fairly flexible.

So these are all possible:

• Asa la mazorca primero.
• Primero, asa la mazorca.

The version with primero at the end is very natural and common. It often sounds like: do this step first, before the others.

Yes. That is also correct.

The difference is mainly one of emphasis and rhythm:

• Asa la mazorca primero = roast the corn first
• Primero asa la mazorca = first, roast the corn

Both are grammatical. The second version puts more focus on the sequence of steps.

It is standard Spanish everywhere as the tú command, not only in Spain.

What is more specifically relevant to Spain is that Spain commonly uses tú and vosotros in everyday speech.

So in Spain you might also hear:

• Asad la mazorca primero = roast the corn first (to more than one person, informal)

Other related command forms are:

• Asa la mazorca primero = to one person, informal
• Ase la mazorca primero = to one person, formal
• Asen la mazorca primero = to more than one person, formal / used in many Latin American varieties for plural you

Asar is a cooking verb. It can mean:

• to roast
• to grill
• sometimes to broil

The exact English translation depends on how the food is being cooked. For corn, roast or grill are often the best choices.

So Asa la mazorca primero could mean something like:

• roast the corn first
• grill the corn first

Here, primero is functioning as an adverb, meaning first.

Compare:

• el primer paso = the first step
  
  • here it works like an adjective
• haz esto primero = do this first
  
  • here it works like an adverb

In Asa la mazorca primero, it tells you when/in what order to do the action.

No, because primero is not describing mazorca here.

It is modifying the action asa: roast first.

So it stays:

• Asa la mazorca primero

If it were directly describing a feminine noun, then you would see agreement:

• la primera mazorca = the first corn cob

But that is not what is happening in your sentence.

In standard Spain pronunciation, asa is pronounced roughly AH-sah.

A few helpful points:

• the a is a clear open vowel, like ah
• the s is a normal s sound
• the stress is on the first syllable: A-sa

Since it ends in a vowel, normal Spanish stress rules put the stress on the second-to-last syllable automatically.

Yes. With affirmative commands, object pronouns are attached to the end of the verb.

For example:

• Asa la mazorca = roast the corn
• Ásala = roast it

Notice that when pronouns are attached, Spanish may add a written accent to keep the stress in the right place:

• asa → ásala

That is a very common pattern with affirmative commands.