That is resumption. So you still have the overhead for the first connection. Assuming that you don't DNS query every few seconds you are gonna suffer.
On a side note, last I checked Quad9 and Cloudflare (need to recheck that) almost immediateley close the connection once you finished your query. Tested with DoT but the same TLS handshake is required for that.
I think you're confused. You're correct that the first connection is 1-RTT but the resumption is a new connection and is 0-RTT using a resumption PSK.
Let's say your browser was left open when you went to work, you get home, click the bookmark for your preferred porn site, and now the browser needs to resolve the FQDN for that site. How fast is that?
So if you have TCP fast open and 0-RTT TLS 1.3 that's exactly one round trip for your answer, just like traditional unencrypted DNS.
The DNS query gets wrapped as an HTTP request, which gets wrapped as a TLS plaintext, which gets sent as TLS 1.3 early data, which all goes in the Fast Open TCP packet.
The server checks the Fast Open cookie, opens the TCP connection, matches the PSK, unwraps the early data, unwraps the HTTP request, unwraps the DNS query
The server finishes the TLS handshake on the now open TCP connection, and using the now encrypted channel it sends back the HTTP response, which wraps a DNS answer and that goes back as the first TCP packet the other way.
Same number of round trips and packets as for DNS. It's very ugly and QUIC in particular will tidy this up considerably, but it's secure and fast.
On a side note, last I checked Quad9 and Cloudflare (need to recheck that) almost immediateley close the connection once you finished your query. Tested with DoT but the same TLS handshake is required for that.