Marta prepara una salsa con poca maionese.

Prepara is the 3rd person singular present tense of preparare (to prepare).

• preparare = infinitive, to prepare
• prepara = he/she prepares or is preparing

Since the subject is Marta, you need the form that matches she:

• Marta prepara = Marta prepares

Italian often leaves out subject pronouns because the verb ending already shows who is doing the action.

• preparo = I prepare
• prepari = you prepare
• prepara = he/she prepares

So Marta prepara is completely natural, and adding lei would usually be unnecessary unless you want emphasis or contrast.

Una is the indefinite article, meaning a or an.

• una salsa = a sauce

Italian often uses the indefinite article where English does too. Saying just salsa without una would sound incomplete in this sentence.

Also, salsa is a feminine singular noun, so it takes una.

Con means with.

Here it introduces the ingredient used to make the sauce:

• una salsa con poca maionese = a sauce with little mayonnaise

This is the normal preposition for saying something is made or prepared with an ingredient.

Because maionese is a feminine singular noun, and poco must agree with it.

Forms of poco:

• poco = masculine singular
• poca = feminine singular
• pochi = masculine plural
• poche = feminine plural

So:

• poca maionese = little mayonnaise

If the noun were masculine, you would use poco:

• poco zucchero = little sugar

After words of quantity like poco/poca, Italian usually does not use an article when speaking generally about an amount of something.

So:

• con poca maionese = with little mayonnaise

If you said con la poca maionese, it would mean something more specific, like:

• with the little mayonnaise (that there is / that we have)

That changes the meaning.

Words like poco, molto, troppo, and other quantity words normally come before the noun in Italian.

So:

• poca maionese
• molto pane
• troppo sale

This is the standard position.

Not exactly.

• poca maionese = little mayonnaise, emphasizing a small amount
• un po’ di maionese = a little mayonnaise or some mayonnaise, often sounding a bit softer or less negative

So poca can suggest not much, while un po’ di often just means some.

It is singular.

When Italian talks about an uncountable substance like mayonnaise, sugar, water, or oil, it usually uses the singular:

• poca maionese
• poco zucchero
• molta acqua

So even though English might think in terms of some mayonnaise, Italian uses the singular noun.

It can mean either, depending on context.

The Italian present tense often covers both:

• Marta prepares a sauce with little mayonnaise
• Marta is preparing a sauce with little mayonnaise

If you want to make the ongoing action especially clear, Italian can also use:

• Marta sta preparando... = Marta is preparing...

But prepara alone is very normal.

Here salsa means sauce.

It is a common Italian noun for many kinds of sauces. The exact type depends on context.

So:

• una salsa = a sauce

It does not necessarily mean the Mexican-style dip called salsa in English.

Yes, but Marta prepara una salsa con poca maionese is the most neutral and natural order.

You could change it for emphasis, for example:

• Con poca maionese, Marta prepara una salsa.

That puts more focus on with little mayonnaise, but the original sentence is the normal default structure:

• subject + verb + object + prepositional phrase

In practice, it relates to the sauce being prepared: a sauce with little mayonnaise.

Grammatically, it comes after una salsa, so most learners should understand it as describing the sauce. In context, it also tells you something about how Marta prepares it.

The natural interpretation is:

• Marta prepares a sauce that contains little mayonnaise.