tomato to tiizu wo tukatta kantanna ryouri ha, isogasii asa de mo sugu taberaremasu.

A helpful way to chunk it is:

[トマトとチーズを使った] [簡単な] 料理 は、[忙しい朝でも] [すぐ] 食べられます。

• トマトとチーズを使った = that uses / made with tomatoes and cheese
• 簡単な = simple
• 料理 = dish / cooking / meal
• は = topic marker
• 忙しい朝でも = even on busy mornings
• すぐ = quickly / right away
• 食べられます = can be eaten / can eat

So the first part, トマトとチーズを使った簡単な料理, is one big noun phrase:
a simple dish made with tomatoes and cheese.

Then the sentence says something about that topic:
it can be eaten quickly even on busy mornings.

Because トマトとチーズ is the object of the verb 使った.

Inside the relative clause:

• トマトとチーズを使った
• literally: used tomatoes and cheese

Japanese relative clauses keep their normal particles. So even though the whole clause modifies 料理, the inside grammar still works normally.

You can think of it like this:

• トマトとチーズを使った料理
• = a dish that used tomatoes and cheese
• more natural English: a dish made with tomatoes and cheese

So を is not marking 料理. It is marking what was used.

Not necessarily. This is a very common point that confuses learners.

使った is the plain past form of 使う, but in a relative clause it often describes a completed relationship, not past time in the overall sentence.

So:

• トマトとチーズを使った料理
• literally: a dish that used tomatoes and cheese
• natural meaning: a dish made with tomatoes and cheese

It does not mean the whole sentence is in the past. The main sentence is still present/non-past because of 食べられます.

A rough comparison in English is how we say:

• the book written by Natsume Sōseki
• the meal made with cheese

Those are past participle-like ideas, even if we are talking about something current.

Because these are two different kinds of adjectives in Japanese.

• 簡単 is a na-adjective
• 忙しい is an i-adjective

Before a noun:

• 簡単な料理 = a simple dish
• 忙しい朝 = a busy morning

So:

• na-adjective + noun → な
• i-adjective + noun → no extra word needed

That is why you get:

• 簡単な料理
• 忙しい朝

not 簡単い料理 and not 忙しいな朝.

は marks トマトとチーズを使った簡単な料理 as the topic of the sentence.

So the feeling is:

• As for simple dishes made with tomatoes and cheese, ...
• When it comes to simple dishes made with tomatoes and cheese, ...

Then the speaker comments on that topic:

• 忙しい朝でもすぐ食べられます

In English we often do not translate は directly, but it helps organize the sentence.

No. Here でも means even.

So:

• 忙しい朝でも
• = even on busy mornings

This is not the sentence-connector でも meaning but / however.

A few similar examples:

• 子どもでもできる = Even children can do it
• 一人でも行きます = I’ll go even alone
• 忙しい朝でも食べられます = You can eat it even on busy mornings

Since 朝 is a time expression, English uses a preposition like on or in, but Japanese just attaches でも directly to the noun phrase.

Here it is understood as potential/possibility:
can eat / can be eaten.

So:

• すぐ食べられます
• = can be eaten quickly
• or in natural English, you can eat it quickly

With 食べる, the form 食べられる can look the same for both:

• potential: can eat
• passive: is eaten

Context tells you which one it is.

In this sentence, the meaning is clearly about convenience or ability, so potential is the natural reading.

Also, because the topic is 料理, English often translates it as can be eaten, even though Japanese does not need to phrase it as a true passive in the same way English does.

Japanese often leaves out the subject when it is obvious or not important.

Here the sentence is making a general statement:

• (you / people / one) can eat it quickly even on busy mornings

The exact eater does not need to be stated. It is understood from context.

This is very common in Japanese. A sentence can sound completely natural without explicitly saying I, you, or people.

すぐ means right away, quickly, or without much delay.

In this sentence, it suggests convenience:

• the dish does not take long before you can eat it
• it is suitable when time is limited

So すぐ食べられます is not really about eating fast with your mouth; it is more like:

• it’s ready to eat quickly
• you can eat it without much delay

Japanese often leaves number unspecified unless it really matters.

So:

• トマト can mean tomato, tomatoes, or tomatoes in general
• 料理 can mean a dish or dishes
• 忙しい朝 can mean a busy morning or busy mornings in general

The translation chooses singular or plural based on what sounds natural in English and what the context suggests.

That is why a sentence like this may be translated with plurals in English even though Japanese does not explicitly mark them.

Sometimes yes, but the nuance is a little different.

• トマトとチーズを使った料理 focuses on a dish made using tomatoes and cheese
• トマトとチーズを使う料理 can sound more like a dish that uses tomatoes and cheese in a general or habitual sense

In many contexts, both might be understandable, but 使った is very natural when describing the ingredients used in a finished dish.

So in this sentence, 使った料理 sounds smooth and natural.