API or template folder redirect in htaccess

Question

I have a directory structure as follows:

.htaccess
api.php
template/index.html

When calling domain.com/api/someendpoint, the request is forwarded to api.php.

# enable apache rewrite engine
RewriteEngine on
# Deliver the folder or file directly if it exists on the server
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_URI} !(.*)/$
RewriteCond %{REQUEST_FILENAME} !-d
# Push every request to api.php
RewriteRule ^(.*)$ api.php [QSA]

now, when calling domain.com, the request should be called to the index.html in the template directory:

RewriteCond %{REQUEST_URI} ^$
RewriteRule . template/index.html [QSA]

this does not work, the directoryListening is always displayed.

What is the correct way to get the index.html?