Whenever I need to write out a simple document wherein content is more important than form, LaTeX is my preferred choice. It beats Google Docs, Microsoft Word, LibreOffice, or any other text processor for that matter.
Overleaf is a solid cloud editor choice these days but I tend to prefer to have full control over my programming environment, thus for a local solution TeXShop is my favorite on macOS:
$ brew install texshop
The following template worked well for me to answer interview questions:
% The next lines tell TeXShop to typeset with xelatex, and to open and save the source with Unicode encoding.
%!TEX TS-program = xelatex
%!TEX encoding = UTF-8 Unicode
\documentclass[12pt, oneside]{article}
\usepackage{geometry}
\geometry{letterpaper}
\usepackage{amssymb}
\usepackage{fontspec,xltxtra,xunicode}
\defaultfontfeatures{Mapping=tex-text}
\setromanfont[Mapping=tex-text]{Hoefler Text}
\setsansfont[Scale=MatchLowercase,Mapping=tex-text]{Gill Sans}
\setmonofont[Scale=MatchLowercase]{Andale Mono}
\title{My document title}
% \author{Thiago Perrotta} % uncomment if applicable
\date{\today}
\begin{document}
\maketitle
\tableofcontents
\pagebreak
\section{Preliminaries}
\paragraph{Foo bar?}
Lorem ipsum.
\paragraph{What is the answer for life, universe and everything?}
42.