You can redirect
https://example.com/, but it means that clear-text HTTP is still being used just to send the HTTP Redirect.
This exposes the user to attacks by tools such as sslstrip, unless he carefully checks every time that the domain is really
https://(insert non-Latin homoglyphs here).com...
In this case, you really want to use HTTP Strict Transport Security:
HTTP Strict Transport Security (HSTS) is a proposed web security policy mechanism where a web server declares that complying user agents (such as a web browser) are to interact with it using secure connections only (such as HTTPS).