[DNS] Review set-up-cname-flattening and add per-record Dash option (#18053)

* Add Dash and API tabs for Per-record CNAME flattening

* Overall text review

* Fix paid accounts to paid zones

* Add API tab to Flatten all CNAMEs section

* Apply suggestion from code review

Co-authored-by: Pedro Sousa <[email protected]>

---------

Co-authored-by: Pedro Sousa <[email protected]>

Author: RebeccaTamachiro

src/content/docs/dns/cname-flattening/index.mdx

@@ -22,9 +22,9 @@ This functionality is also what allows you to use a [root custom domain](/pages/
 
 With `CNAME` flattening, Cloudflare finds the IP address that a `CNAME` points to. This process could involve a single lookup or multiple (if your `CNAME` points to another `CNAME`). Cloudflare then returns the final IP address instead of a `CNAME` record, helping DNS queries resolve up to 30% faster.
 
-For more details on the mechanics of `CNAME` flattening, review the [CNAME flattening diagram](/dns/cname-flattening/cname-flattening-diagram/) and refer to the [Cloudflare blog post](https://blog.cloudflare.com/introducing-cname-flattening-rfc-compliant-cnames-at-a-domains-root/).
+For more details on the steps involved in `CNAME` flattening, review the [CNAME flattening diagram](/dns/cname-flattening/cname-flattening-diagram/) and refer to the [Cloudflare blog post](https://blog.cloudflare.com/introducing-cname-flattening-rfc-compliant-cnames-at-a-domains-root/).
 
 ## Aspects to keep in mind
 
-* `CNAME` flattening happens by default in some cases, as explained in its [Setup page](/dns/cname-flattening/set-up-cname-flattening/)
+* `CNAME` flattening happens by default in some cases. Refer to [Setup](/dns/cname-flattening/set-up-cname-flattening/) for details.
 * <Render file="cname-flattening-callout" />

src/content/docs/dns/cname-flattening/set-up-cname-flattening.mdx

@@ -9,7 +9,7 @@ head:
 
 ---
 
-import { Render } from "~/components"
+import { Render, TabItem, Tabs, GlossaryTooltip } from "~/components"
 
 :::note
 
@@ -25,24 +25,51 @@ If the `CNAME` target is on the same zone as the `CNAME` record, Cloudflare proc
 
 ## For all CNAME records
 
-Accounts on paid plans can choose to flatten all `CNAME` records on their domain. This option is useful for DNS-only (unproxied) `CNAME` records since proxied records are flattened by default (as they return Cloudflare IPv4 and IPv6 addresses).
+For zones on paid plans, you can choose to flatten all `CNAME` records. This option is useful for <GlossaryTooltip term="proxy status">DNS-only (unproxied)</GlossaryTooltip> `CNAME` records. [Proxied records](/dns/manage-dns-records/reference/proxied-dns-records/#proxied-records) are flattened by default as they return Cloudflare anycast IPs.
+
+<Tabs syncKey="dashPlusAPI"> <TabItem label="Dashboard">
 
 1. Log in to the [Cloudflare dashboard](https://dash.cloudflare.com/login) and select your account and domain.
 2. Go to **DNS** > **Settings**.
-3. For **CNAME Flattening**, select **Flatten all CNAMEs**.
+3. Turn on the option **CNAME flattening for all CNAME records**.
+
+</TabItem> <TabItem label="API">
+
+Make a `PATCH` request to the [Update DNS Settings](/api/operations/dns-settings-for-a-zone-update-dns-settings) endpoint and set `flatten_all_cnames` to `true` in the request body.
+
+</TabItem> </Tabs>
 
 :::caution
  <Render file="cname-flattening-callout" />
 :::
 
 ## Per record
 
-Accounts on paid plans also have the option to flatten specific `CNAME` records. This operation is currently only supported via API.
+Paid zones also have the option of flattening specific `CNAME` records.
+
+<Tabs syncKey="dashPlusAPI"> <TabItem label="Dashboard">
+
+1. Log in to the [Cloudflare dashboard](https://dash.cloudflare.com/login) and select your account and domain.
+2. In **DNS** > **Settings**, make sure that **CNAME flattening for all CNAME records** is turned off.
+3. Go to **DNS** > **Records** and find the `CNAME` record you would like to flatten.
+4. Select **Edit** and turn on the **Flatten** option.
+5. Select **Save** to confirm.
+
+:::note[Unavailable flatten option]
+For the following cases, **Flatten** will not be available:
+- The record is at the [zone apex](#for-your-zone-apex).
+- The record is already proxied, which means it will be flattened by default.
+- **CNAME flattening for all CNAME records** is turned on, which means you cannot override it per record.
+:::
+
+</TabItem> <TabItem label="API">
 
 With the available [API endpoints](/api/operations/dns-records-for-a-zone-create-dns-record), specify the following for each `CNAME` record in the request body:
 
 ```txt
 "settings": {
   "flatten_cname": true
 }
-```
+```
+
+</TabItem> </Tabs>

src/content/partials/dns/cname-flattening-callout.mdx

@@ -3,4 +3,4 @@
 
 ---
 
-If a `CNAME` target is being used to verify a domain for a third-party service, enabling the [Flatten all CNAMEs](/dns/cname-flattening/set-up-cname-flattening/#for-all-cname-records) setting may cause that functionality to work incorrectly since the `CNAME` record itself will not be returned directly.
+If a `CNAME` target is being used to verify a domain for a third-party service, turning on [CNAME flattening for all CNAME records](/dns/cname-flattening/set-up-cname-flattening/#for-all-cname-records) may cause the verification to fail since the `CNAME` record itself will not be returned directly.