Q:

Why is the first cell offset in this latex table? 

The following is a MWE from a much larger table where I cannot get the first cell to align with the rest of the title row.   

\documentclass{article}

 \usepackage[T1]{fontenc}
\usepackage[default]{lato}
\usepackage{tabu}
\usepackage{xcolor}
\usepackage{graphicx}

\usepackage{geometry}
\geometry{left=2cm,right=2cm,marginparwidth=7cm,marginparsep=2cm,top=1.25cm,bottom=1.25cm,footskip=2\baselineskip}

\definecolor{accent}{HTML}{020e17}
\definecolor{emphasis}{HTML}{000000}
\definecolor{body}{HTML}{000000}
\definecolor{default}{HTML}{000000} 

\colorlet{accent}{accent}
\colorlet{emphasis}{emphasis}
\colorlet{body}{body}

\begin{document}

\begin{center}

{\color{emphasis}
\resizebox{\textwidth}{!}{%
\renewcommand{\arraystretch}{1.3}
 \begin{tabu}{| >{\raggedright\arraybackslash} p{0.20\linewidth}   p{0.8\linewidth} | } 

 \hline
 \rowfont{\color{accent}} \rule{0pt}{2ex}  
        Title 1 & Title 2                        \\ %[0.5ex] 
 \hline
 \rowfont{\color{body}} \rule{0pt}{2ex}
    desc 1

    & bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla blabla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla blabla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla  \\    

       \rowfont{\color{body}} \rule{0pt}{2ex}
  Product Oversight and Improvement

  &bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla 
  bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla blabla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla blabla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla \\ \rowfont{\color{body}} \rule{0pt}{0ex} ~&~\\

 \hline
\end{tabu}}}
\end{center}

A:

Instead tabu table environment I would rather use tabularx:
\documentclass{article}
\usepackage[hmargin=2cm,
            marginparwidth=7cm,marginparsep=2cm,
            vmargin=1.25cm,
            footskip=2\baselineskip
            ]{geometry}
\usepackage[T1]{fontenc}
%\usepackage[default]{lato}
\usepackage{ragged2e}
\usepackage{cellspace, tabularx}
\setlength\cellspacetoplimit{5pt}
\setlength\cellspacebottomlimit{5pt}
\addparagraphcolumntypes{X}
\usepackage{xcolor}
\definecolor{accent}{HTML}{020e17}
\definecolor{emphasis}{HTML}{000000}
\definecolor{body}{HTML}{000000}
\definecolor{default}{HTML}{000000}

\colorlet{accent}{accent}
\colorlet{emphasis}{emphasis}
\colorlet{body}{body}
\usepackage{graphicx}

%---------------- show page layout.  don't use in a real document! 
\usepackage{showframe}
\renewcommand\ShowFrameLinethickness{0.15pt}
\renewcommand*\ShowFrameColor{\color{red}}
%---------------------------------------------------------------%
\usepackage{lipsum}

\begin{document}
    \begin{center}
\begin{tabularx}{\linewidth}{|>{\RaggedRight\hsize=0.34\hsize}X
                             |>{\RaggedRight\hsize=1.66\hsize}SX
                             |}
    \hline
Title 1 & \textcolor{accent}{Title 2}      \\
    \hline
desc 1  & \lipsum*[11]  \\
Product Oversight and Improvement
        & \lipsum*[12]  \\
    \hline
\end{tabularx}
    \end{center}
\end{document}

which gives:

(red lines indicate text borders)

As you can see, for more vertical space above/below cells' contents is obtain by use of cellspace package, which define S column modifier. 
Using of thet now has some fixes, but it is still not regularly maintained  tabu package is still fragile (as far as I know).  
\rowfont is not intended for changing font colors, bit for font families, font shapes and text alignment in cells (see page 3 of the package documentation)
Your use of \rule add some vertical space above cells contents but not belos of the, for this you should write for example \rule[-1ex]{0pt}{3ex}
In your table design I would rather use rules from the package booktabs and remove vertical lines:

\documentclass{article}
\usepackage[hmargin=2cm,
            marginparwidth=7cm,marginparsep=2cm,
            vmargin=1.25cm,
            footskip=2\baselineskip
            ]{geometry}
\usepackage[T1]{fontenc}
%\usepackage[default]{lato}
\usepackage{ragged2e}
\usepackage{booktabs, tabularx}
%---------------- show page layout.  don't use in a real document! 
\usepackage{showframe}
\renewcommand\ShowFrameLinethickness{0.15pt}
\renewcommand*\ShowFrameColor{\color{red}}
%---------------------------------------------------------------%
\usepackage{lipsum}

\begin{document}
    \begin{center}
\begin{tabularx}{\linewidth}{@{} >{\RaggedRight\hsize=0.34\hsize}X
                                 >{\RaggedRight\hsize=1.66\hsize}X
                             @{}}
    \toprule
Title 1 & Title 2       \\
    \midrule
desc 1  & \lipsum*[11]  \\
    \addlinespace
Product Oversight and Improvement
        & \lipsum*[12]  \\
    \bottomrule
\end{tabularx}
    \end{center}
\end{document}

