I noticed that my latest blog post wasn't showing the Nunjucks code within markdown code blocks. Turns out you need to escape Nunjucks code if you are using nunjucks templates. 😁
Found a solution by Mark Llobrera - Eleventy: Escaping Nunjucks Statements in Markdown Code Blocks
{% raw %}{% if postImage %}
<meta name="twitter:image" property="og:image" content="{{ site.cloudinary_url }}{{ postImage }}" />
{% endif %}{% endraw %}