Terraform: Conditional creation of a resource based on a variable in .tfvars

Add a count parameter with a ternary conditional using the variable declared in .tfvars like this:

resource "cloudflare_record" "record" {
  count = var.cloudflare ? 1 : 0
  zone_id = "${data.cloudflare_zones.domain.zones[0].id}"
  name    = "${var.subdomain}"
  value   = "${var.origin_server}"
  type    = "CNAME"
  ttl     = 1
  proxied = true
}

In this example var.cloudflare is a boolean declared in the .tfvars file. If it is true a count of 1 record will be created. If it is false a count of 0 record will be created.

After the count apply the resource becomes a group, so later in the reference use 0-index of the group:

cloudflare_record.record[0].some_field