You can’t use interpolation in a tfvars file.
Instead you could either join it directly in your Terraform like this:
terraform.tfvars
hosted_zone = "example.com"
domain = "my"
main.tf
resource "aws_route53_record" "regional" {
zone_id = data.aws_route53_zone.selected.zone_id
name = "${var.domain}.${var.hosted_zone}"
type = "A"
ttl = "300"
records = ["4.4.4.4"]
}
Or, if you always need to compose these things together you could use a local:
locals {
domain = "${var.domain}.${var.hosted_zone}"
}
resource "aws_route53_record" "regional" {
zone_id = data.aws_route53_zone.selected.zone_id
name = local.domain
type = "A"
ttl = "300"
records = ["4.4.4.4"]
}