Demander is the infinitive of the verb.

Therefore: to ask.

It was hard to get used to. I write a polite request for something and the machine translation looks as if I am rudely demanding something.

I wonder if your reversal is accurate:

🇫🇷 demander : 🇬🇧 to ask

To ask could be to ask a question, so I would say “to request” or “to place an order” would seem more accurate.

Missed my favorite one:

🇬🇧 demand: 🇫🇷 exiger 🇫🇷 demander : 🇬🇧 to ask

This one is the source of endless confusion...