Brett-EDH
TVWBB Olympian
Flap: https://en.wikipedia.org/wiki/Flap_steakNot sure what flap mat is up here.....I do know many of our cuts are called something different below the boarder.
My 3 main cuts that I use for things other than steaks or roasts are......
Flank, which might be similar to what you have there but your beef looks a bit different.
Picanha and skirt.
I picked up a black angus skirt a few months back tossed it in the freezer........
The marbling and fat on this thing makes yours look like a center cut roast for Italian sandwiches. Like a top sirloin.....
Couldn't believe it, so I had to buy it.
Just kidding thou yours looks insane good, I really haven't come across anything like this I can buy...but I will talk to my beef butcher.
I don't really know what to use this skirt on, thinking either cutting it into shorter pieces as it is about a foot and a half long and making tacos or leaving it and trying it in fajita's.
I gotta get pics of this thing and show it off.
When I use flank for street taco type cooks I use a reposado with lime and cumin......among others.
This is a very distinct flavour and is addictive......keep it in mind......but as far as going traditional Mexican flavors I don't do that.
Flank: https://en.wikipedia.org/wiki/Flank_steak
Skirt: https://en.wikipedia.org/wiki/Skirt_steak
I used to like flank but only use it for sandwiches now. It’s just too dry and doesn’t have richness in flavor. Not enough fat in it for my liking.
For carne asada, flap or skirt are best. Skirt is more expensive and fattier but both are great tasting beef strips. Only cook them less than medium so they retain their juices. Both cuts absorb marinades and flavors well. And their fat gives up a nice char while still remaining juicy.
Picanha is best for direct heat seared small steak chunks then sliced for eating. This cut has substantial beef flavor and I wouldn’t add anything to it except kosher salt. It really stands on its own and deserves a nice wine with it.
I use top sirloin in Asian cooking. Searing in a hot wok, thinly sliced. And I’ll grind some with chuck for a drier burger, more like a 80/20 to a 90/10 burger. This cut would also make a decent steak but again, it enough fat in so so you’d have to be cautious to not dry if out over coals.
Hopefully these links help you with your butcher.