As America’s Jewish delis fade from storefronts, a century-old restaurant at Montreal — Schwartz’s Deli — serves up the past one “smoked meat” sandwich at a time, offering a delicious connection to the past on paper placemats.

Tzach Yoked wrote in Haaretz that in the 1930s, there were 1,500 Jewish delis at New York City, but that by 2018, they’d fallen to just 20, a number further eroded by the pandemic and as neighborhood tastes changed.

The most famous remnant of Gotham’s Jewish culinary past, Katz’s Deli, benefits from having appeared in “When Harry Met Sally,” but with sandwiches running around $26, it has priced out many diners it once served.

Schwartz’s serves about 1,000 pounds of its beef brisket a day within walls adorned by photographs, memorabilia. Reader’s Digest named it among “the Best of Canada,” but it hasn’t had to go Hollywood to survive.

A sandwich runs just $13.75 Canadian, about 10 bucks American. Pickles, sauerkraut, and coleslaw cost a few extra “loonies” — the nickname for Canada’s dollar coin, featuring a loon.

The deli is still where Reuben Schwartz opened it in 1928 on St. Laurent Boulevard, the city’s main street, untouched by the construction on all sides. That it’s free of the graffiti tags that mar much of Montreal speaks to the respect residents have for it.

I set out to investigate how Schwartz’s endured while other delis have had to close or franchise to survive. “First of all,” Schwartz’s general manager, Frank Silva, told me, “we’ve had only a few owners, and whoever buys into this place sees the bottom line and doesn’t want to change anything.”

After arriving from Romania, Schwartz concocted a secret blend of local herbs and spices — available for purchase — and laid down the process: Meat is marinated for 10 days, smoked overnight, steamed all day, and sliced à la minute by hand.

“We produce the product in-house,” Mr. Silva said. “Everything’s done the same way as Mr. Schwartz did in 1928. We don’t open three or four places because then you lose control. We don’t have a master kitchen somewhere else. It’s here. We don’t have a freezer in the house because everything’s fresh.”

The result is a savory, moist sandwich different from pastrami or corned beef yet just as satisfying. Diners may not be able to finish more than one, but they can purchase vacuum-sealed smoked meat to try and recreate the magic at home.

“Even vegetarians eat it,” Mr. Silva said. “You know how many vegetarian reporters come here? I say, ‘How are you going to write a story if you don’t try it?’ Once they try it, they have to cheat, and this is the place to cheat. There’s nothing better.”

Like Schwartz, the two owners who followed had no heirs, making the dedication to keeping the same menu and resisting modernization a marvel. There’s no credit card machine, either. Cash or debit only.

Fans of the formula run from gourmands like Anthony Bourdain — who, Mr. Silva says, “used to eat here all the time” — to singer Celine Dion, a silent partner since 2012 and an icon in Quebec, the French-speaking province of which Montreal is the largest city.

Everyone from the baseball slugger Henry “Hank” Aaron, the actor Burt Lancaster, the comedian Jerry Lewis — not to mention a panoply of hockey legends — has squeezed into stools at the counter or into tables, although it’s not a simple matter of driving the six hours due north from Katz’s for a pickup. The hungry often line up outside to wait.

Online orders are the only visible sign that Schwartz’s operates in the 2020s and not the 1920s. Behind the scenes, when wood-burning and charcoal-burning grills weren’t up to code, they were replaced, but advancements like the state-of-the-art, stainless-steel smokehouse haven’t changed the taste.

Google where to eat at Montreal, Mr. Silva said, “and we show up at the top.” It’s a place of honor the deli has earned by serving sandwiches from yesterday made fresh today — ones it’s well worth crossing the border to experience for yourself.