@SLB
can you cut the lamb in 1/2 , so you get to try two different things ?
there is probably a thicker part
abd a thinker lower part
cut it so the two pieces might be of different thickness ,
but each one is a similar thickness .
you will have a better chance of getting the doneness in each to your liking
What is ' mexican ' to you ? for me , its cumin . toast some cumin , cool and grind.
or get a fresh unopened jar
then get some good quality single chile powder you could make your own
but Id use that. a fresh jar
then think about fresh additions , after the powder and salt ( to you taste )
you can salt on your plate , remember refrigerate for a day
open flat on a rack in your oven, pick a temp that gets you the inner tamp you like
rest , thinly carve . add the diced up fresh : cilantro leaves ? onion ? Line juice ?
sound like a very interesting project.
plus post pics ?