J’aime la tarte quand elle reste moelleuse au milieu et croustillante sur les bords.

Because je becomes j’ before a vowel sound.

• je aime is not used
• it becomes j’aime

This is called elision. French often drops the final vowel of a short word before a following vowel or silent h.

Other examples:

• j’adore
• j’habite
• l’école

La tarte is being used in a general sense. In French, when you talk about liking something in general, you usually use the definite article:

• J’aime la tarte = I like pie / I like tart

This is different from English, which often uses no article:

• I like pie
• but in French: J’aime la tarte

Compare:

• J’aime le chocolat = I like chocolate
• J’aime les pommes = I like apples

If you said une tarte, it would usually mean a specific tart rather than tart in general.

Here, quand means when.

The sentence is saying that the speaker likes tart when it has a certain texture:

• quand elle reste moelleuse... = when it stays soft...

It introduces a time/condition idea: the tart is liked in the situation where it remains soft in the middle and crisp at the edges.

French could also use lorsqu’ in some contexts, but quand is very common and natural here.

Elle refers to la tarte.

Since tarte is a feminine singular noun, the pronoun that replaces it is also feminine singular:

• la tarte → elle

So:

• J’aime la tarte quand elle reste... means:
• I like tart when it stays...

In English, we use it for things, but in French, nouns have grammatical gender, so a thing can be referred to as il or elle depending on the noun.

Rester means to remain or to stay.

So:

• elle reste moelleuse = it stays soft / it remains soft

This is slightly different from:

• elle est moelleuse = it is soft

Using reste emphasizes that the texture continues to be that way, rather than simply describing it. In a food context, that makes a lot of sense: the tart keeps a soft middle and crisp edges.

Because these adjectives describe la tarte, which is feminine singular.

French adjectives usually agree with the noun they describe:

• masculine singular: moelleux, croustillant
• feminine singular: moelleuse, croustillante

So:

• la tarte est moelleuse
• la tarte est croustillante

Even though the adjectives come after reste, they still describe la tarte, so they must agree with it.

Moelleuse means something like:

• soft
• tender
• moist
• sometimes fluffy or pillowy, depending on context

For food, it usually suggests a pleasant soft texture, not dry or hard.

In this sentence, moelleuse au milieu means the tart is soft or tender in the center.

Au milieu means in the middle or in the center.

The word au is a contraction of:

• à + le = au

Even though milieu is masculine (le milieu), the whole expression au milieu is very common and fixed.

So:

• au milieu = in the middle
• au centre = in the center

In this sentence:

• moelleuse au milieu = soft in the middle

Sur les bords means on/at the edges.

• les bords is plural because a tart has multiple edges or all around its outer edge.
• French often uses the plural here where English might say around the edges or at the edges.

So:

• croustillante sur les bords = crisp on the edges / around the edges

This sounds natural in French.

French often avoids repeating words that are already understood.

So:

• elle reste moelleuse au milieu et croustillante sur les bords

is a shorter way of saying:

• elle reste moelleuse au milieu et elle reste croustillante sur les bords

Both parts describe the same subject, elle. Since the verb reste still applies, it does not need to be repeated.

This kind of omission is very common in French and English:

• The tart is soft in the middle and crisp at the edges.

You would not usually repeat is there either.

Yes. J’aime is the present tense of aimer, and here it expresses a general liking or preference.

So:

• J’aime la tarte... = I like tart...

It does not necessarily mean the speaker is eating it right now. It can simply describe what they like in general.

French uses the present tense this way very often:

• J’aime le café.
• Je préfère le thé.
• J’adore les gâteaux maison.

A natural pronunciation would sound roughly like:

jem la tart kan el rest mwaløz o milyeu ay کروstillant sur lé bor

More carefully:

• J’aime → sounds like jem
• quand elle → often flows together smoothly
• moelleuse → a tricky word; the oeu sound is rounded
• au milieu → o milyeu
• et croustillante → the t in et is usually not pronounced here
• les bords → the final s in les is usually silent, and bords ends with a pronounced r

A useful tip: try to say the sentence in smooth chunks:

• J’aime la tarte
• quand elle reste moelleuse au milieu
• et croustillante sur les bords

That will sound more natural than pronouncing each word separately.