Hoy quiero preparar una tortilla de patata con jamón para la cena.

Because Spanish often drops subject pronouns when the verb already shows who is doing the action.

• quiero = I want
• So yo quiero and quiero both mean I want

In this sentence, quiero already tells you the subject is I, so yo is not necessary.

You could say:

• Hoy yo quiero preparar...

but it sounds more emphatic, as if you were stressing I.

After querer when you mean to want to do something, Spanish uses:

• querer + infinitive

So:

• quiero preparar = I want to prepare

The second verb must stay in the infinitive form, which here is preparar.

More examples:

• Quiero comer = I want to eat
• Quiero salir = I want to go out
• Quiero estudiar = I want to study

So quiero preparo is not correct.

Una is the feminine singular indefinite article, meaning a / an.

• tortilla is a feminine noun
• So it takes una

That gives:

• una tortilla = an omelette / a tortilla

Spanish nouns have grammatical gender, so the article must match the noun:

• un libro
• una casa
• una tortilla

In Spain, tortilla usually means an omelette, especially a thick Spanish-style one.

So in this sentence:

• tortilla de patata = Spanish potato omelette

This is not the same as the flat corn or flour tortilla common in Mexican food.

That difference is very important:

• In Spain: tortilla often means omelette
• In much of Latin America / English: tortilla usually means the flat bread

Spanish often uses de to show what something is made of or contains.

So:

• tortilla de patata = potato omelette
• literally, omelette of potato

This pattern is very common:

• zumo de naranja = orange juice
• bocadillo de jamón = ham sandwich
• sopa de verduras = vegetable soup

In English we often put the ingredient before the noun; in Spanish, de is very common for this.

Because this sentence is in Spanish from Spain.

In Spain:

• patata = potato

In many Latin American countries:

• papa = potato

Both are correct Spanish, but patata is the usual word in Spain.

Both can be heard in Spain.

• tortilla de patata
• tortilla de patatas

Both refer to the same dish.

Why the variation?

Spanish can talk about ingredients in either singular or plural, depending on usage and regional preference. In real life, both versions are common. Many learners first hear tortilla de patatas, but tortilla de patata is also very natural.

So this sentence is perfectly fine.

It describes the tortilla.

So the idea is:

• a potato omelette with ham

The structure is:

• una tortilla de patata = a potato omelette
• con jamón = with ham

Together:

• una tortilla de patata con jamón

So the ham is an added ingredient in the omelette.

Because para is used here to express purpose or intended use.

• para la cena = for dinner
• meaning: it is intended to be eaten at dinner

Para often means:

• for
• in order to
• intended for

Examples:

• Esto es para ti = This is for you
• Estudio para aprender = I study in order to learn
• Preparo algo para la cena = I prepare something for dinner

Por would not fit this meaning.

In Spanish, meals are often used with the definite article:

• el desayuno
• la comida
• la cena

So:

• para la cena = for dinner

This is very natural Spanish. English often omits the article, but Spanish commonly includes it.

Compare:

• Desayuno a las ocho = I have breakfast at eight
• para el desayuno = for breakfast
• para la cena = for dinner

Putting Hoy first is very natural because it sets the time frame right away:

• Hoy = today

So the sentence starts by telling you when this intention applies.

Spanish word order is flexible, and you could also say:

• Quiero preparar hoy una tortilla de patata con jamón para la cena

But starting with Hoy sounds very natural and often helps organize the sentence clearly.

Yes, but the meaning changes slightly.

• para la cena = for dinner
• esta noche = tonight

So:

• Hoy quiero preparar una tortilla de patata con jamón para la cena
  = Today I want to prepare a potato omelette with ham for dinner.

• Hoy quiero preparar una tortilla de patata con jamón esta noche
  = Today I want to prepare a potato omelette with ham tonight.

The first focuses on the meal.
The second focuses on the time of day.

Both can work, but para la cena fits the original idea better.

Yes, very often.

Both are natural:

• Quiero preparar una tortilla...
• Quiero hacer una tortilla...

The difference is small:

• preparar = to prepare
• hacer = to make

In everyday speech, hacer una tortilla is extremely common.
Preparar can sound a little more like prepare, but it is also completely normal.

Usually yes, jamón means ham, but in Spain it can also carry a strong cultural association with Spanish cured ham.

Depending on context, it might mean:

• cooked ham
• cured ham
• serrano ham
• another kind of ham

If you want to be more specific, Spanish can say:

• jamón serrano
• jamón ibérico
• jamón cocido

But by itself, jamón is a perfectly normal general word for ham.

Yes, very natural.

Everything in it sounds normal for Spain:

• Hoy
• quiero preparar
• una tortilla de patata
• con jamón
• para la cena

It is a straightforward everyday sentence a Spanish speaker in Spain could easily say.