yasai wo yoku niru to, suupu no azi ga yoku narimasu.

No. In this sentence, と is a conditional particle, not and.

野菜をよく煮ると、スープの味がよくなります。 means something like:

• If/when you simmer the vegetables well, the soup tastes better
• When vegetables are cooked well, the soup’s flavor improves

With a verb before it, と often expresses:

• a natural result
• a general truth
• something that tends to happen

So this sounds less like a one-time event and more like a general cooking fact.

It is the same word, but it works a little differently in each place.

1. よく煮る

   • here よく means well, thoroughly, or for a good amount of time
   • so よく煮る = simmer/boil well

2. 味がよくなります

   • here よく comes from the adjective いい / よい
   • よくなる means become good or more naturally become better

So:

• 野菜をよく煮る = cook the vegetables thoroughly
• 味がよくなります = the flavor gets better

Because 野菜 is the direct object of 煮る.

• 煮る = to boil, simmer, cook in liquid
• What are you simmering? 野菜
• So: 野菜を煮る

The particle を marks the thing that the action is done to.

Because 味 is the thing that becomes better.

In スープの味がよくなります:

• スープの味 = the soup’s taste / the flavor of the soup
• が marks that as the subject of よくなります
• よくなる is an intransitive expression: something becomes good/better

So the structure is:

• the soup’s flavor
  • becomes better

That is why が is used, not を.

Because the sentence is describing a change of state, not someone actively making something better in a direct grammatical sense.

• よくなる = to become good / to improve
• よくする = to make something good / to improve something

Here, Japanese naturally says:

• スープの味がよくなります
• the soup’s flavor improves

Even though in English we might also say cooking the vegetables well makes the soup taste better, Japanese often uses the become pattern here.

Because the sentence is focused more on the action and result than on setting up a topic with は.

The particles already show the roles clearly:

• 野菜を = vegetables as the object
• スープの味が = the soup’s flavor as the subject of the result

You could create other versions with は, but this sentence is perfectly natural as it is.

For example:

• 野菜はよく煮ると、スープの味がよくなります

This might sound like as for vegetables, if you simmer them well..., but the original is more neutral and straightforward.

It literally means the taste of the soup or the soup’s flavor.

The particle の connects nouns and often shows possession or relation.

So:

• スープ = soup
• 味 = taste, flavor
• スープの味 = the soup’s taste / flavor

This is a very common noun-linking pattern in Japanese.

Both can be natural, but they are slightly different in nuance.

• 味がよくなります focuses on the flavor
• おいしくなります means becomes delicious / tastier

So:

• スープの味がよくなります = the soup’s flavor improves
• スープがおいしくなります = the soup becomes tastier

The version with 味 sounds a bit more specific and descriptive, especially in a cooking explanation.

This is very normal in Japanese.

When a verb comes before a particle like と, it usually stays in plain form:

• 煮ると

The politeness of the whole sentence is usually shown at the end:

• なります

So this mix is standard:

• plain form in the subordinate clause
• polite form in the main clause

This does not sound inconsistent to Japanese speakers.

It can mean boil, but in many cooking contexts it is better understood as simmer or cook in liquid.

That is important because English boil can sound very strong, while Japanese 煮る often covers gentler cooking in liquid too.

In this sentence, a natural interpretation is:

• simmer the vegetables well
• cook the vegetables thoroughly in the soup

That fits the idea of improving the soup’s flavor.

This is a very common question.

• 煮る = simmer, stew, cook in liquid, often as part of a dish
• 茹でる = boil something in water, often just to cook that item itself

So if vegetables are cooked in a soup and their flavor affects the soup, 煮る is the better choice.

Examples:

• 野菜をスープで煮る = simmer vegetables in soup
• 野菜をお湯で茹でる = boil vegetables in hot water

In your sentence, 煮る fits because the soup’s flavor changes as a result.

It sounds like a general rule or usual result.

That is largely because of the conditional と. This pattern often expresses:

• what generally happens
• a natural consequence
• something reliable or typical

So the feeling is:

• When you simmer vegetables well, the soup tastes better
• If vegetables are cooked thoroughly, the flavor improves

It does not strongly sound like a one-time event from a story.

The subject is simply not stated, because Japanese often leaves it out when it is obvious or unimportant.

In English, we often want a subject like:

• you
• we
• someone

But Japanese does not need to say that here. The sentence is about the cooking process and the result, not about who does it.

So the understood meaning is something like:

• If you simmer the vegetables well, the soup tastes better
• When vegetables are simmered well, the soup’s flavor improves

Both are reasonable ways to understand it.

The comma is mainly there to make the sentence easier to read.

It separates:

• the condition: 野菜をよく煮ると
• the result: スープの味がよくなります

Japanese commas are often used more flexibly than English commas. The sentence could still be understandable without it, but the comma helps show the break between the two parts.