Japoix 975 Lincoln St., 303-861-2345, japoix.com

The showstopper at Japoix is neither the hot rock (sashimi-style meat cooked at the table on a 1,000-degree volcanic rock), nor the tempura rock shrimp. It’s the ahi burger, a stunning slab of ruby-red, just-seared tuna and a brilliant tangle of red cabbage slaw. The secret, according to executive chef Jay Spickel-mier, lies in the multiple layers of flavor: the togarashi-rubbed tuna steak, the quick-pickled cucumbers, the braised cabbage, and the spicy Sriracha aïoli, all sandwiched on a fresh-baked bun. But, perhaps surprisingly, it’s the tangy, house-made mustard that ties all the flavors together. For the condiment, Spickelmier toasts fresh mustard seeds to bring out their natural oils before tenderizing them in a reduction of cider vinegar and Asian spice blend. To further soften the seeds, he lets the mixture sit for a week before puréeing it in the food processor. The result is a freshness and a vibrancy not found in premade mustards. When the sandwich arrived at our table, before even a first bite, all conversation stopped. And we’re guessing the same will happen when you order this extraordinary “burger.”