Railway does not publish a static IP, so an A record is not an option. Apex domains require CNAME flattening or a dynamic ALIAS/ANAME record, and AWS Route 53 does not support either. While the zone lives on Route 53 the apex cannot point at Railway. Two ways forward: serve the site from www (which takes an ordinary CNAME) and use Route 53 to redirect the apex to it, or move the zone's nameservers to a provider that supports flattening, such as Cloudflare.