\documentclass[11pt]{book}
\usepackage{calc}
\usepackage{enumitem}
\usepackage{xepersian}
\settextfont[Scale=1]{Tahoma}
\setlatintextfont[Scale=1]{Times New Roman}
\setdigitfont[Scale=1]{Tahoma}
\makeatletter
\bidi@patchcmd{\@Alph}{آ}{الف}
{\typeout{Succeeded in changing `آ` into `الف`}}
{\typeout{Failed in changing `آ` into `الف`}}
\makeatother
\begin{document}
 \begin{enumerate}[label=\Alph*)]
 	\item \lr{1}
 	\item \lr{2}
 \end{enumerate}
\end{document}