Learn Hardcore Portuguese (Portugal): Hoje não quero nem micro-ondas nem fogão; vou comer frio. - Today I want neither microwave nor stove; I’m going to eat cold.

No. European Portuguese has negative concord: multiple negative elements co‑occur to express a single negation. With verbs like querer, you normally say Não quero nem X nem Y. You can drop não only if you front the whole nem … nem … phrase for emphasis: Nem micro-ondas nem fogão quero (usar) hoje.

Do I have to repeat nem before both items?

Yes, that’s the natural pattern: nem X nem Y. With longer lists, keep repeating it: Não quero nem micro-ondas nem fogão nem forno. Omitting the second nem is possible in some styles, but repeating it is safest and most idiomatic.

Can I use ou or e instead of nem ... nem?

Not if you want the meaning of “neither … nor.”

ou means “or” and, under negation, can be ambiguous; avoid it here.
e means “and,” so Não quero micro-ondas e fogão suggests you don’t want both together, not necessarily each one individually.
Use não … nem … nem … to be clear.

Why is there no article before micro-ondas or fogão? Should it be o micro-ondas, o fogão?

Both are possible. Without articles you’re speaking generically: Não quero usar micro-ondas nem fogão (no microwave or stove in general). With articles you’re likely referring to specific appliances: Não quero usar o micro-ondas nem o fogão. In European Portuguese, articles are frequent, but in bare lists/generic statements they’re often dropped.

How do I spell and pluralize micro-ondas? What’s its gender?

Standard spelling is micro-ondas (with hyphen; AO 1990).
It’s masculine: o micro-ondas.
The plural is invariable: os micro-ondas, dois micro-ondas.
Avoid forms like microondas or microonda.

What exactly does fogão mean? Is it “stove” or “oven”?

In Portugal:

fogão traditionally refers to a freestanding cooker (hob + oven).
In many kitchens today you have a separate placa (hob) and forno (oven).
If you specifically mean you won’t use the hob or the oven, you can say nem a placa nem o forno. The sentence with fogão is still understood as “no stove/cooker.”

Does quero here mean “I want [a microwave]”? Where is “to use”?

Context supplies the missing verb; it’s ellipsis. Hoje não quero nem micro-ondas nem fogão is shorthand for Hoje não quero usar nem o micro-ondas nem o fogão. Portuguese often omits obvious complements like usar in everyday speech.

Why use vou comer instead of the simple future comerei or the present?

ir + infinitivo (here, vou comer) is the most common way to express near future/intent in speech. Alternatives:

Como frio (present with future value; also fine: scheduled/decided action).
Comerei frio (simple future; more formal/literary in Portugal).
Avoid vou a comer (not idiomatic for near future). Estou a comer means “I’m eating (now).”

Is comer frio correct? Should frio agree with the food?

With no explicit object, frio is used as a predicate adjective by default (masculine singular): Vou comer frio = “I’ll eat it cold.” If you mention or pronominalize the object, make it agree:

Vou comer a sopa fria. / Vou comê-la fria.
Vou comer o bife frio. / Vou comê-lo frio.

Where do object pronouns go with vou comer? Is vou comê-lo right?

In European Portuguese, with ir + infinitivo you normally attach the clitic to the infinitive: Vou comê-lo frio / Vou comê-la fria. Spelling note: comê-lo / comê-la takes a circumflex to keep the stress. Placing the clitic with the auxiliary (Vou-o comer) is possible but sounds very formal/rare in modern EP.

Why a semicolon? Could I use a comma, a dash, or a period?

A semicolon neatly separates two closely related independent clauses: … fogão; vou comer frio. A period also works: … fogão. Vou comer frio. A dash is conversational: … fogão — vou comer frio. A bare comma between independent clauses is less formal and best avoided in careful writing.

Can I move hoje? Is Hoje não quero … different from Não quero … hoje?

Both are fine and mean the same. Hoje não quero … fronts the time frame and is very natural in Portuguese. Não quero … hoje is also common. Choose based on rhythm/emphasis.

How do I pronounce the tricky words in European Portuguese?

Approximate EP pronunciations (caps show the stressed syllable):

Hoje: OH-zh(uh) [silent h; final vowel reduced]
não: nãw (nasal “ow”)
nem: nehm (nasal)
micro-ondas: mee-kruh-ÓN-dash (final -s ≈ “sh” in EP)
fogão: foo-GOWN (nasal “ão”)
vou: voh
comer: koo-MEHR (tapped r)
frio: FREE-oo (i + o glide)

Is nem ... nem only used with querer?

No. It’s general:

Não uso nem o micro-ondas nem o fogão.
Não vou aquecer nem no micro-ondas nem no fogão.
Ela não come nem carne nem peixe.

Would Brazilians say this the same way?

The structure não … nem … nem … is the same. Differences:

Pronoun placement: in Brazil, enclisis to the infinitive (vou comê-lo) is formal; colloquially many say vou comer ele/a or repeat the noun.
Progressive: Brazil uses estar + gerúndio (estou comendo), while Portugal uses estar a + infinitivo (estou a comer).
Pronunciation differs (final -s not “sh” in most of Brazil).