Terraform: how to read list of maps?

The trick here is to use the dictionary syntax to replace the element call, it behaves better with lists of maps.

value = "${lookup(data.aws_kms_secrets.api_key.*.plaintext[count.index], "secret_name")}"

its tempting to do data.aws_kms_secrets.api_key[count.index].plaintext that isn't valid HCL