The Terraform documentation for acm_certificate_validation only supports a single domain in the request. This module allows you to support multiple domains in the request as long as they are the APEX or *.APEX domain. This will reduce code complexity and cost by allowing you to have a single certificate with more domains.
resource "aws_acm_certificate" "certificate" { domain_name = "mydomain.dev" validation_method = "DNS" subject_alternative_names = [ "*.mydomain.dev", "myseconddomain.co", "*.myseconddomain.co", "*.mythirddomain.co.uk" ] } module "acm-multiple-domains" { for_each = {for domain in aws_acm_certificate.certificate.domain_validation_options: domain.domain_name => domain} source = "cebollia/acm-multiple-domains/aws" version = "1.0.0" certificate_arn = aws_acm_certificate.certificate.arn domain = each.key name = each.value.resource_record_name type = each.value.resource_record_type record = each.value.resource_record_value ttl = 3600 } resource "aws_acm_certificate_validation" "validate" { certificate_arn = aws_acm_certificate.certificate.arn validation_record_fqdns = [for domain in module.acm-r53-records : domain.record.fqdn ] }