Улий, вот классические пирожки (с фруктами): https://e1.edimdoma.ru/data/recipes/0003/2327/32327-ed4_wide.jpg
Они тоже fruit pie? Или есть другой вариант?

Yep, if there’s dough on the outside and fruit on the inside - it’s a fruit pie)))

We have the same thing: https://happyspeedy.com/content/hostess-fruit-pie-cherry-45oz

If it is big and we have to cut it into small pieces we call it пирог. When it is a small single piece enough for one eater to eat at a time we call it пирожок. You use one word for either of them?

Yes. We have the word PIELET or TARTLET, but it refers to a small individual pie that looks exactly like a large one - in a round aluminum pan, with a fancy crust, etc.

tartlet — тарталетка
Strange but English borrowed "pirog" (пирог) from Russian as well as "pierogi" (пироги) from Polish with a bit different meaning. And "pirozhok" (пирожок) in addition. And all of them have a good variety of spellings.

I see and some dictionaries say that "pielet n. (rare) a small pie". None of the Russian dictionaries that I have know that word. Is this word really rare and unpopular?

No. Every time you look at a catering menu at a convention center or other meeting facility, they offer pielets and cookies. I also saw it on the menu for the private plane (which is cute, because you can have a pielet and a pilot all in one craft))) I also saw Pecan Pielets for sale in a diner when I was driving to New Orleans last time.

Now I see. It looks like actual life and dictionaries here go wide apart. 😊

you can have a pielet and a pilot all in one craft

You were full of craft to have so many [ˈpaɪləts] at once. 😉

when I was driving to New Orleans last time.

It is the second time when I hear about New Orleans today. The first was “A large river-boat was going down the Mississippi on its way to New Orleans.” (I hope you read “Uncle Tom’s Cabin” :)

Hahaha, I live in New Orleans and Florida, and sometimes when I go to New Orleans, I drive instead of fly. 😉