Section header and landscape-oriented figure on same PDF page - r

Question

Inside a knitr-generated PDF, I want to have the section title on the same page as a figure displayed in landscape format.
If I do this
---
title: "Untitled"
output: pdf_document
date: '2022-06-21'
header-includes:
- \usepackage{pdflscape}
---
# Section title
\begin{landscape}
```{r pressure, out.extra= 'angle=0', echo = F}
plot(pressure)
```
\end{landscape}
The plot appears on a different page than "Section title" as \begin{landscape} apparently starts a new page
But if I do this
---
title: "Untitled"
output: pdf_document
date: '2022-06-21'
header-includes:
- \usepackage{pdflscape}
---
\begin{landscape}
# Section title
```{r pressure, out.extra= 'angle=0', echo = F}
plot(pressure)
```
\end{landscape}
I am getting an error message
! You can't use `macro parameter character #' in vertical mode.
l.74 #
Section title
Error: LaTeX failed to compile sectionTitle.tex. See https://yihui.org/tinytex/r/#debugging for debugging tips. See sectionTitle.log for more info.
Execution halted
Edit: this syntax, leaving empty lines around the section heading, is not working
---
title: "Untitled"
output: pdf_document
date: '2022-06-21'
header-includes:
- \usepackage{pdflscape}
---
\begin{landscape}
# Section title
```{r pressure, echo=FALSE}
plot(pressure)
```
\end{landscape}