After some more searching on the web it looks like Powershell can be an easy solution (for the output file I use the Default encoding the machine instead of "ascii" as I need to preserve the Cyrillic characters). Guess will go with the below:

 Code:
gc -en utf8 utf8.txt | Out-File -en default out.txt


or this

 Code:
[io.file]::ReadAllText("c:\kix\utf8.txt", [System.Text.Encoding]::utf8) | %{[io.file]::WriteAllText("c:\kix\out.txt", $_, [System.Text.Encoding]::Default)}