Not having any leftover flank steak (again), I took this dish back a little closer to its "stuffed pepper" roots by using hamburger left over from taco night yesterday. I was fully expecting not to be wowed by this recipe, I mean boiled onions, c'mon. However, I was pleasantly surprised-- the onions retained their crunch and the meaty filling with salty cheese and spices was really tasty. To my surprise, my husband had seconds. Not bad for leftovers! My daughter liked playing with the tiny onions that popped out from the middle of the onion. The red onion did not retain much color (the purple pigments, anthocyanins, are water soluble), but the white onions had a lovely pearly white color, which I rather preferred.