Unfortunately I deleted my WebApp, A domain which was purchased through azure portal by following these steps
https://azure.microsoft.com/en-us/documentation/articles/custom-dns-web-site-buydomains-web-app/
Was attached with this webapp. Now that I don't have any access to domain's DNS, If I visit my domain it says
This page is parked free, courtesy of Azure
How I can get my domain back to me.
You haven't lost your domain, so there's no getting it back to you. The issue is that you deleted your web app, so Azure is providing a default landing page for your now-unused domain name.
If you create a new web app, and want to assign your domain name to it, you should be able to in the Custom Domains and SSL blade for that web app's configuration.
For example, here's the settings for one of my web apps. I'd see my purchased domain names under Managed Domains.
