Top Chef Masters — What’s a vegan doing on a gourmet cooking show?

There’s probably no client more terrifying to a master chef than a vegan … who is gluten-intolerant … and doesn’t eat soy.

Such was the challenge on the latest edition of Top Chef Masters. The final five contestants met up with the lovely and talented Zooey Deschanel, who conveniently stars in “(500) Days of Summer,” which opens in theaters this weekend.

Deschanel — a doppelganger of singer Katy Perry — got to host a five-course dinner party of friends, family and food critics. This collision of foodies and food-needies resulted in one of the more compelling episodes of the season.

The quickfire challenge really set the mood, with the competitors — Rick Bayless, Michael Chiarello, Hubert Keller, Anita Lo and Art Smith — asked to concoct their version of a cheeseburger and fries. Considering French master Keller actually serves a burger at his Las Vegas restaurant that costs $5,000, it was a no-brainer that the eventual delights were on an elemental plane rungs higher than a fast food chain.

Special guest Morgan Spurlock — who was famously banished for a month to his own gastronomic plane of hell in the documentary “Super Size Me” — was among those lucky enough to judge the burgers. These ranged from the grand “best burger ever” of Chiarello to the too-clever-but-not-quite-as-yummy cheese soup and burger bites courtesy of lowest-ranked Lo.

Then it was on to Deschanel, who couldn’t have come across sweeter and more “into the show.” Although, you couldn’t help but wonder what a painful experience it would be for someone with her dietary restrictions to watch Top Chef every week (as she claimed).

Chiarello summed up her eating habits best when he said, “It’s all about ‘no.’ It’s off-putting to say the least.”

Under these cuisine handcuffs, certain chefs thrived.

Bayless pointed out how easily Mexican fare (his specialty) fit into such parameters, offering a dish anchored by corn tamales and black beans. French-trained Keller made a trio of picturesque delights involving gazpacho, beet salad and asparagus. Chiarello delivered a pasta made from quinoa (a grain-like crop with edible seeds) that looked and apparently tasted like a dish served at the most high-end of Italian eateries.

The other masters appeared rather baffled by the challenge.

Lo went with a grilled eggplant that was a visually dull contribution for someone who has proven so innovative and artful throughout the season.

Judge Jay Rayner commented, “Vegan food is usually a symphony of beige.” This dish fit right into his pre-meal statement.

Faring worse was weepy chef Smith, who went with a pre-made rice ice cream as the central element of his dessert course. While he tried to dress it up with fresh strawberries and a side of homemade almond brittle, the crowd was not wowed. Suggestions ranged from “he instead should have used coconut milk” (uttered by a diner) to “I should have made a sorbet” (uttered by Smith).

While Deschanel raved about the experience, saying, “It’s so rare that I get to eat anything other than raw vegetables,” the reality of the reality competition show was that somebody needed to be sent packing.

A half star difference separated loser Smith and almost-loser Lo. Despite his heartbreaking loss, it was one of the few occasions when Smith didn’t cry.

The real winners were the vegans everywhere, who now have concrete proof that meals don’t have to look and taste like rabbit food.