Translation:The restaurant has pastas and pizzas.
"Restoracio" appears in Zamenhof's Fundamento de Esperanto but is translated into English as "eating-house" — reminding me perhaps that restaurants weren't all that common in the late 19th and early 20th century, at least not in the way we think of them today. The Esperanto root comes from the Polish word, "restauracja," which maybe Zamenhof was more familiar with at the time.
Certainly "manĝejo" exists and is used a lot. Depending on the context, I would call it a dining hall or a dining room. There are lots of words that exist in Esperanto (and have existed for over 100 years) which cause new learners to stop and ask "why do we need this ballast?" My short answer to this question is that the word is already international, so a form of it belongs in Esperanto. Also, there is a certain kind of activity which happens in restaurants which doesn't happen in dining halls and chow houses.
I agree, or rather expect both to be acceptable, especially since in other lessons, similar words were introduced whose plural could acceptably be simply the word itself again. For example, in the lesson where "frukto" was introduced, both "fruit" and "fruits" were acceptable translations of "fruktoj".
They probably just missed that "pasta" does also have a countable form, when it means "kind of pasta", as in "we have wide selection of pastas".
On the other hand, one cannot say "I have 17 pastas on my plate" (when there is only one kind of pasta there, and one is referring to the number of physical items there), so it's easy to forget that there isn't only the more common uncountable form.
I disagree. "Fruktoj" is a very clear example where the countability is different in English and Esperanto. "Frukto" means "a single piece of fruit" and that it well established. On the other hand, "pastajxo" is not in that category. I would understand "tiu restoracio havas pastajxojn kaj picojn" to mean that they sell pasta dishes and whole pizzas (possibly single-serving pizzas."