How to align beamer slide content with markdown pandoc?

I use markdown to generate beamer slides with pandoc.

This markdown…

# Test

foobar

…is compiled to this Latex:

begin{frame}{Test}
  protecthypertarget{test}{}
  foobar
end{frame}

What do I have to write in Markdown to align the content to the bottom, i.e. getting this output?

begin{frame}[b]{Test}
  protecthypertarget{test}{}
  foobar
end{frame}

P.S. I’m aware of this question which asks for another case of marking a frame. Unfortunately it was wrongly closed as a duplicate.

# Test {.b}

foobar

begin{frame}[b]{Test}
protecthypertarget{test}{}
foobar
end{frame}