No almoço de hoje, nós comemos grão-de-bico com tomate.

No is a contraction of em + o.

• em = in / at / on
• o = the

So no almoço literally looks like in the lunch, but in natural English it means at lunch or during lunch.

This kind of contraction is very common in Portuguese:

• em + o = no
• em + a = na
• de + o = do
• a + o = ao

So No almoço de hoje means At today’s lunch / During today’s lunch.

Portuguese usually expresses this idea with noun + de + time expression.

So:

• o almoço de hoje = today’s lunch
• a aula de amanhã = tomorrow’s class
• a reunião de ontem = yesterday’s meeting

Literally, de hoje means of today, but in English we normally translate it more naturally as today’s.

The phrase No almoço de hoje is an introductory time expression, and Portuguese often separates that kind of phrase with a comma.

So the sentence structure is:

• No almoço de hoje, = time frame
• nós comemos grão-de-bico com tomate. = main clause

The comma helps readability and makes the pause clear. In informal writing, you may sometimes see the comma omitted, especially in short sentences, but using it here is perfectly normal.

Usually, no.

Portuguese often leaves out subject pronouns because the verb ending already shows who the subject is.
Comemos already tells you the subject is we.

So both are possible:

• No almoço de hoje, nós comemos grão-de-bico com tomate.
• No almoço de hoje, comemos grão-de-bico com tomate.

In European Portuguese, omitting nós is often more natural unless you want:

• emphasis
• contrast
• extra clarity

For example:

• Eles comeram peixe, mas nós comemos grão-de-bico.

Here nós is useful because it contrasts with eles.

It can mean either one, depending on context.

For comer, the 1st person plural form is spelled the same in the present and the preterite:

• nós comemos = we eat
• nós comemos = we ate

So how do you know which one it is?
You use context.

In this sentence, No almoço de hoje strongly suggests a specific completed meal, so the most natural reading is:

• we ate

This is a very common feature of Portuguese verbs.

Because in Portuguese, food items are often named in the singular when referring to them as an ingredient or food type.

So:

• comer grão-de-bico = to eat chickpeas / chickpea
• gosto de tomate = I like tomato / tomatoes
• comprar batata = to buy potatoes / potato

When you are talking about the food in a general or ingredient sense, the singular is very common.

If you want to emphasize separate individual chickpeas, the plural grãos-de-bico is also possible. But in everyday food descriptions, grão-de-bico is very natural.

Because grão-de-bico is a fixed compound noun in Portuguese, and its standard spelling includes hyphens.

It is treated as one lexical item, not just three separate words.

Singular:

• grão-de-bico

Plural:

• grãos-de-bico

Notice that only grão changes to plural; the rest stays the same.

Here tomate is being used as an ingredient name, so the singular is very natural.

Portuguese often uses the singular for ingredients or food substances:

• massa com tomate
• arroz com frango
• pão com queijo

So com tomate means something like with tomato in it / with tomato as an ingredient.

If you say com tomates, it suggests actual tomatoes as separate items or pieces, rather than tomato as a general ingredient.

After com, Portuguese often uses a bare noun when talking about ingredients or accompaniment in a general sense.

So:

• com tomate
• com queijo
• com arroz

This sounds like with tomato / with cheese / with rice as part of the dish.

If you say com o tomate, that usually refers to a specific tomato already known from context:

• Comemos o peixe com o tomate da horta.
• We ate the fish with the tomato from the garden.

So in your sentence, no article is the normal choice.

Yes, No almoço de hoje is natural and understandable in European Portuguese.

That said, in Portugal a very common everyday alternative would be:

• Hoje ao almoço, comemos grão-de-bico com tomate.

Both are good, but they feel slightly different:

• No almoço de hoje = at today’s lunch; a bit more descriptive or framed
• Hoje ao almoço = today at lunch; very common and conversational in Portugal

So if your goal is natural European Portuguese, Hoje ao almoço... is a very useful pattern to learn too.

Because no almoço and para o almoço do different jobs.

• no almoço = at lunch / during lunch
• para o almoço = for lunch

In your sentence, you are describing when the eating happened, so no almoço is the right choice.

Compare:

• No almoço de hoje, comemos grão-de-bico com tomate.
  = At today’s lunch, we ate chickpeas with tomato.

• Para o almoço de hoje, fizemos grão-de-bico com tomate.
  = For today’s lunch, we made chickpeas with tomato.

So para is more about purpose or planning, while no is about the occasion/time.