Like most guys out there, I use cloudflare for my DNS which works quite well and has extra features you can play with.
One of the feature is what they call Page Rules, which allow you forward or redirect one or more secondary domains to a primary domain.
Follow the steps below to redirect or forward a domain.
1. Log into your Cloudflare account.
2. Select Website from the dropdown menu on the top left, then select the domain you want to forward.
3. Select the Page Rules tab.
4. Create Page Rule.
5. Enter the URL of the domain you want to forward in this format. *secondarydomain.com/
6. Click + Add a Setting and select Forwarding URL from the drop-down.
7. Select 301 – Permanent Redirect from the Select Status Code tab.
8. Enter destination URL. http://primarydomain.com/
9. Save and Deploy.
Just wait for some minutes before trying out the domain redirect.
You can repeat this step to forward as many secondary domains to a primary domain.
Feel free to reach out on the comment section if you are having issues setting up.