Overlined capital letter with small parenthesis

You can use the stackengine package. Ignore all the commands in the example, I only used those to typeset a compact example.

The commands that are important for you are

% PREAMBLE
\newcommand\brabar{\scalebox{.3}{(}\raisebox{-1.7pt}{--}\scalebox{.3}{)}} 

% DOCUMENT
\stackon[.1pt]{<letter>}{\brabar}

\documentclass{article}
\usepackage{geometry}
\usepackage{stackengine}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{mathtools}
\usepackage{pgffor}

\newcommand\brabar{\scalebox{.3}{(}\raisebox{-1.7pt}{--}\scalebox{.3}{)}}

\begin{document}
\newgeometry{textwidth=3.5cm}
\foreach \lett in {A,B,C,...,Z}{
\noindent\stackon[.1pt]{\lett}{\brabar}
}
\restoregeometry
\end{document}

With this code?

\documentclass[a4paper]{article}
\usepackage[english]{babel}
\usepackage[utf8x]{inputenc}
\usepackage{amsmath}
\usepackage{graphicx}
\usepackage{accents}
\newcommand\brabar{\scalebox{.3}{(}\raisebox{-1.7pt}{$-$}\scalebox{.3}{)}}
\newcommand\brobor{\smash[b]{\raisebox{0.6\height}{\scalebox{0.5}{\tiny(}}{\mkern-1.5mu\scriptstyle-\mkern-1.5mu}\raisebox{0.6\height}{\scalebox{0.5}{\tiny)}}}}

\begin{document}

\[
\overset{\brabar}{D}\phantom{}^{0}
\]


\[
\accentset{\brobor}{D}\phantom{}^{0}
\]

\end{document} 

The main problem is that -- is asymmetrical and $-$ is contained in a very large box. One can demonstrate this using \fbox with \fboxsep=0pt.

\documentclass{standalone}
\usepackage{mathtools}
\newcommand\brabar{\scalebox{.3}{(}\raisebox{-1.7pt}{$-$}\scalebox{.3}{)}}

\newcommand\brabarb{\scalebox{.3}{(}\raisebox{-1.7pt}[0pt][0pt]{$-$}\scalebox{.3}{)}}

\begin{document}
$
\overset{\brabar}{D}\phantom{}^{0}  
\overset{\brabarb}{D}\vphantom{D}^{0}
$
\end{document}