Force non-www and https via htaccess

Based on Gumbo's comment : "the TLS/SSL connection is established and certificate is validated before it is handed down to HTTP and the HTTP redirection takes place" I gave this a try (which seems to work):

RewriteEngine On 
RewriteCond %{SERVER_PORT} 80 
RewriteRule ^(.*)$ https://www.blahblah.com/$1 [R,L]

RewriteCond %{HTTP_HOST} ^www\.blahblah\.com [NC]
RewriteRule ^(.*)$ https://blahblah.com/$1 [L,R=301]

please tell me if there is something wrong with this approach.

The only set of rules that works for me is the following

# match any URL with www and rewrite it to https without the www
    RewriteCond %{HTTP_HOST} ^(www\.)(.*) [NC]
    RewriteRule (.*) https://%2%{REQUEST_URI} [R=301,L]

# match non https and redirect to https
    RewriteCond %{HTTP:X-Forwarded-Proto} !https
    RewriteRule ^(.*)$ https://%{HTTP_HOST}/$1 [R=301,L]

The order matters, it prevents a third redirect in some cases.

Try this rule:

RewriteCond %{HTTP_HOST} ^(www\.)(.+) [OR]
RewriteCond %{HTTPS} off
RewriteCond %{HTTP_HOST} ^(www\.)?(.+)
RewriteRule ^ https://%2%{REQUEST_URI} [R=301,L]