HDFC BizMoney Back will let you buy Amazon Pay vouchers via
SmartBuy + Gyftr at net 2% OFF (there is a 2.5% + GST upfront surcharge and a 5% subsequent cashback) which can in turn be used for Insurance, IRCTC and even Utilities payments (though for Utilities you have one of the best cards in the form of Axis ACE).
For Flipkart, Myntra, BigBasket, Swiggy/Zomato there is no surcharge and thus you can get them at 5% OFF using the same route as above.
SmartBuy is a platform only for display of offers extended by Merchants to HDFC Bank's Customers
offers.smartbuy.hdfcbank.com
If you are interested in Tata Neu Coins instead of the cashback (I see no reason why anyone would do this) refer to this table -
SmartBuy is a platform only for display of offers extended by Merchants to HDFC Bank's Customers
offers.smartbuy.hdfcbank.com