Below steps tested with Tomcat 9.0.11 on both Windows & Linux machine.
Open command prompt/terminal and execute below keytool command to create a new key store with a self-signed certificate by replacing the alias and keystore values.
keytool.exe -genkey -alias <<certaliasname>>-keyalg RSA -keystore <<location to save keystore>>\<<keystorename>>
provide the details of the certificate as it asks questions.
Open server.xml file from <<TOMCAT_HOME>>/conf/ location
and add below text by replacing keystoreFile and keystorePass values.
<Connector port="8443" protocol="org.apache.coyote.http11.Http11NioProtocol"
maxThreads="150" SSLEnabled="true" scheme="https" secure="true"
clientAuth="false" sslProtocol="TLS"
keystoreFile="<<path to keystore file>>"
keystorePass="<<keystore password>>" />
then restart the tomcat server and access https://<<hostname>>:8443
Thanks!