No sabes lo buena que sale la tortilla cuando la patata está bien cocida.

Yes, literally it means You don’t know..., but in Spanish this is often used idiomatically for emphasis, especially before lo + adjective + que.

So No sabes lo buena que sale... really means something like:

• You have no idea how good ... turns out
• You don’t know how good ... is

It is a very natural way in Spanish to sound expressive.

This is an exclamative/intensive structure:

• lo + adjective + que + verb

It means how + adjective in English.

So:

• lo buena que sale la tortilla = how good the tortilla turns out

You will see this pattern a lot:

• No sabes lo difícil que es. = You don’t know how difficult it is.
• Mira lo grande que está. = Look how big it is.
• No sabes lo bien que canta. = You don’t know how well she sings.

Good question. In this structure, lo is a neuter element used to introduce the degree or quality, but the adjective still agrees with the noun it describes.

Here, buena describes la tortilla, which is feminine singular, so the adjective must also be feminine singular:

• la tortilla → buena

That is why you get:

• lo buena que sale la tortilla

Compare:

• No sabes lo bueno que está el café.
  (bueno agrees with el café)
• No sabes lo buena que está la sopa.
  (buena agrees with la sopa)

Yes, salir often means to go out / to leave, but it also has another very common meaning: to turn out, especially with food, recipes, plans, or results.

So in cooking:

• La tortilla sale muy buena. = The omelette turns out very good.
• El bizcocho salió perfecto. = The cake turned out perfect.

In this sentence, sale means:

• turns out
• comes out

This is very natural Spanish.

Sometimes yes, but the nuance is slightly different.

• sale buena = turns out good / comes out good
• queda buena = ends up good / tastes good / is good as a result

Both can work in many cooking contexts, but salir is especially common when talking about how a dish turns out after making it.

So:

• La tortilla sale muy buena sounds very natural.
• La tortilla queda muy buena also sounds natural.

They are close, but sale often feels a bit more like the final outcome of the preparation.

In Spanish from Spain, tortilla usually means omelette, not the flatbread.

In this sentence, because it mentions la patata, it almost certainly refers to tortilla de patatas or Spanish omelette.

So for a learner of Spanish from Spain, tortilla often means:

• omelette
• especially Spanish potato omelette

Whereas in many Latin American contexts, tortilla may refer to the flatbread.

Spanish often uses the singular to talk about an ingredient in a general sense.

So:

• cuando la patata está bien cocida

means something like:

• when the potato is properly cooked
• when the potato in the dish is well cooked
• when the potatoes are cooked properly in a general ingredient sense

Using the singular here treats patata as the ingredient as a whole, not as individual potatoes.

You could hear las patatas too in other contexts, but the singular is very natural when talking about an ingredient generically.

Bien cocida means well cooked or properly cooked.

• bien = well / properly
• cocida = cooked

Here cocida comes from the verb cocer, which means to cook in the sense of boiling or cooking through until soft.

In the context of tortilla de patatas, this suggests that the potato is cooked enough, soft enough, and done properly before finishing the tortilla.

Both come from different verbs:

• cocer → cocido/a
• cocinar → cocinado/a

The difference is roughly this:

• cocido/a focuses on being cooked through
• cocinado/a is broader and means cooked/prepared

For potato in a tortilla, bien cocida is more precise, because the important point is that the potato is properly cooked and tender.

So:

• la patata está bien cocida = the potato is properly cooked through

That sounds more natural here than bien cocinada.

Because this is talking about a state or result after cooking, not a permanent characteristic.

• estar + past participle/adjective often describes a resulting condition
• ser would sound wrong here because being cooked is not an inherent, defining quality of the potato

So:

• la patata está bien cocida = the potato is well cooked

This is a temporary/resulting state, so estar is the natural choice.

Sale is the third person singular present tense of salir.

• yo salgo
• tú sales
• él/ella sale

Here the subject is la tortilla, so:

• la tortilla sale

The present tense is often used for general truths, habits, or typical results, so the sentence means something like:

• The tortilla turns out really good when the potato is properly cooked

It is not necessarily about one specific tortilla only; it can express a general rule.

Spanish often places the whole clause after the exclamative structure:

• lo buena que sale la tortilla

Literally, this is closer to:

• how good the tortilla turns out

English and Spanish organize this kind of idea differently. In Spanish, the structure naturally builds like this:

1. lo
2. buena
3. que
4. sale la tortilla

So even if it feels unusual from an English perspective, it is standard Spanish word order.

You can understand it word for word, but a natural English translation is usually better.

A very literal breakdown would be:

• No sabes = You don’t know
• lo buena que = how good
• sale la tortilla = the tortilla turns out
• cuando la patata está bien cocida = when the potato is well cooked

But natural English would be:

• You have no idea how good the tortilla turns out when the potato is properly cooked.

So for learning purposes, it is useful to know the pieces, but for translation, it is better to choose natural English rather than a strict word-for-word version.