Tuna tostadas are a cool, crispy, restaurant-style dish to make at home

By G. Daniela Galarza / The Washington Post

Earlier this year, I was out with friends for dinner at Pascual, a fun Capitol Hill restaurant run by chefs Isabel Coss and Matt Conroy. (They are also the team behind Georgetown’s Lutèce.) My friend was put in charge of ordering for our table of four, so when the waiter returned with our drinks, he rattled off a list of plates we’d share.

“And the tuna tostada?” he asked. “We want the tuna tostada, too, right?”

Of course we did. Seemingly moments later, it arrived on an eggshell-white stoneware plate: a blue corn tostada spread with a thin layer of avocado, topped with fat slices of precisely cut tuna, plus bits of citrus, onions and herbs. It took us no time to finish, so we ordered another.

Looking around the dining room, my friend pointed out that every table within view had also ordered the tostada. It’s a straightforward dish, found along the coast in Mexico, but also in restaurants in Mexico’s central cities.

Why, I wondered, hadn’t I made fresh tuna tostadas at home?

I decided to talk to Coss about her approach.

“We almost always have it on the menu if tuna is in season,” she told me. “It’s such a classic Mexican dish, but it translates so well.”

She noted that people who aren’t as familiar with Mexican food are just as likely to order it as people who have been eating Mexican food their whole lives.

“We even put it on the menu at Lutèce, because we missed cooking Mexican food,” Coss said with a little laugh. “But [at Pascual], it changes here and there, depending on the tuna we get, yellowfin or bluefin. I like it with a salsa macha, with a crunch, and avocado. I love fat on fat. Right now we have it with a pistachio salsa macha, tomatoes and tuna. It goes so well.”

How hard would it be to recreate this restaurant standard at home? My local grocery store had sushi-grade tuna steaks in the freezer section, so I grabbed them, along with a package of tostadas, a few avocados, limes, a bag of tangerines, a serrano chile and a bunch of cilantro.

When I got home, I put a couple of the vacuum-packed tuna steaks in a bowl of cold water and assessed the avocados. I remembered that a tuna tostada I’d had at Lutèce tasted of miso and mustard, so I mashed the avocado with mild shiro miso and punchy Dijon.

This tasted great on its own, but it needed some acidity. Lime juice made it pop. At this point, the tuna was partially defrosted  — an ideal state for slicing it thinly with a sharp knife.

Pascual’s tuna seemed to glisten in the light, so I put the slices in a bowl with a little olive oil and tangerine juice while I worked on the other components.

Coss mentioned that they’d once gotten mandarinquats from a local farmer and used them, thinly sliced, on top of each tostada. I cut half a tangerine into itty-bitty triangles to use as a garnish, along with very thinly sliced serrano.

Time to taste-test: I spread a tostada with the miso-mustard guacamole. Then, I shingled tuna slices on top, just like they did at the restaurant, and carefully arranged a few tangerine bits and sliced chiles on the tuna. I added cilantro leaves and a sprinkling of toasted sesame seeds to get at the crunch that Coss said she likes so much.

Feeling fancy, I plucked a few baby nasturtium leaves off my porch plant and added those, too. Then I took a bite.

The buttery tuna played well with the spicy avocado and serranos. The miso and sesame added their grounding flavors, while the citrus made each crunchy bite come alive. I ate two for dinner that night while standing at my kitchen counter.

One would make a lovely lunch, I think, or a fine pairing with something more substantial — perhaps a verdant posole? Or a humble bowl of beans if you’re especially hungry.

Tuna Tostadas

These no-cook tostadas feature thinly sliced sushi-grade tuna atop mashed avocado that’s seasoned with white miso, Dijon mustard and citrus juice.  A single tostada makes a nice appetizer; for a more filling meal, serve these as part of a spread of small bites.

If using frozen tuna, submerge it in a bowl of cold water for 15 minutes to partially defrost, but be sure to use right away.

The tuna tostadas are best as soon as they are made. Sushi- or sashimi-grade tuna can be found at fish markets and in the freezer section of well-stocked supermarkets. Ready-made tostadas can be found at Latin markets or well-stocked supermarkets.

1 small tangerine or mandarin orange, such as a clementine, halved

1 tablespoon extra-virgin olive oil

12 ounces sushi- or sashimi-grade tuna steaks, fresh or, if frozen, partially defrosted 

Flesh of 1 ripe Hass avocado

1 tablespoon fresh lime juice (from ½ to 1 lime)

1 tablespoon shiro (white) miso

½ tablespoon Dijon mustard, plus more as needed

4 (5- or 6-inch) tostadas 

1 serrano chile, seeded, if desired, and thinly sliced, for serving, optional

Fresh cilantro, nasturtium or microgreen leaves, for serving

Toasted sesame seeds, for serving

Flaky sea salt, for serving

Juice half of the tangerine; you should have at least 1 tablespoon.

In a medium shallow bowl, mix together the juice and olive oil.

Place the tuna on a cutting board and, using a very sharp knife, thinly slice the fish against the grain. (This is easier to do if it’s still partially frozen; once sliced, it will fully defrost quickly.) Transfer slices to the bowl with the juice mixture and toss to coat.

In a small bowl, use a fork to mash the avocado with the lime juice, miso and mustard until mostly smooth. Taste and add additional mustard, if desired. You should have about 1 cup.

Thinly slice the remaining tangerine half, then cut each slice into tiny wedges.

Use a small spoon to spread about ¼ cup of the avocado mixture across each tostada. Arrange tuna slices on top, shingling them neatly, if desired. Garnish each tostada with the tangerine wedges, serrano slices, if using, cilantro, sesame seeds and a pinch of flaky salt.

Serve immediately.

Serves 2-4.