While top sirloin is more tender, both should be marinated in an acid type of fluid. Citrus or vinegar based marinade to soften the connective tissue. A simple red wine vinegar with olive oil, salt and garlic powder marinade is really yummy.

...we used Coca-Cola as a tenderizer for steaks. The head cook told me that Pepsi left an aftertaste. I couldn't tell you if that was true or not, but I've used Coke that way many times since. It seems to work.

It was too tough to eat!

And I thought I was hungry.

Not even Mr. Silver the cat in interested ... humph he says!

Garbo can I guess .......................

decades ago, because of similar problems.

If I want a steak, I'll go to a restaurant.

then it’s inedible? Been there done that.

can be good as a fast hot cook steak but it is risky, better for marinating first.
guarantee tender, get tenderloin or filet mignon.
almost foolproof but can be a bit fatty get a ribeye. a high grade new york strip is sometimes a little cheaper and can be pretty good.
most other cuts that are "steak" take more experience to do right.

cooking technique matters too. you can ruin good meat by cooking it wrong.
steak should be rare to med rare for best results and a thermometer is the best way to tell. even if further cooking is desired, a thermometer is the best way to not ruin a cut of expensive meat.

"Run the cow past the grill to scare it, then cut off a slab." (Yeah, he likes it REALLY rare.) He's also said if the vet can't save it, it's overcooked.