Smoked Salmon Roll-Up

Directions

1. To make the cake: Center a rack in the oven and preheat the oven to 400°F. Coat a rimmed baking sheet that’s about 12 × 17 inches with baker’s spray, line it with parchment paper and spray the paper. Have a clean kitchen towel and a strainer at hand.
2. Stir the poppy seeds and garlic and onion powder together in a small bowl.
3. Sift the flour and cornstarch together onto a sheet of parchment paper (easy to use later as a funnel) or into a medium bowl.
4. Put the whites in the bowl of a stand mixer fitted with the whisk attachment, or in a large bowl you can use with a hand mixer, and put the yolks in another large bowl. Whisk the yolks with the salt and lemon zest.
5. Beat the whites at medium-high speed until they hold firm peaks, taking care to stop before they separate into puffs. Spoon about a quarter of the whites over the yolks, add the lemon juice and whisk to blend—you’re using the whites here to lighten the yolks, so there’s no need to be gentle. Sprinkle the poppy seed mixture over the yolks, scrape the remainder of the whites into the bowl and top with the dry ingredients. Working with a flexible spatula, gingerly fold everything together, turning the bowl as you fold and being on the lookout for pockets of flour—they have a habit of hiding at the bottom of the bowl. The mixture will deflate—it’s inevitable—so just carry on.
6. Scrape the batter out onto the parchment-lined baking sheet and spread it evenly across the entire surface.
7. Bake for 6 to 8 minutes, or until the cake has puffed (it will puff unevenly) and the top feels dry to the touch. Transfer the baking sheet to a rack and immediately, while the cake is still hot, lay the kitchen towel out on a work surface and dust it with cornstarch—shake the cornstarch through the strainer onto the towel. Run a table knife around the edges of the baking sheet to loosen the cake and turn it out onto the towel. Lift off the baking sheet and very carefully peel away the parchment. If necessary, turn the towel so that a short side of the cake is parallel to you (if you prefer a longer, more slender cake, you can roll it up starting from a long side), and roll the cake up as tightly as possible in the towel. Twist the ends of the towel to compress the cake, then allow to cool to room temperature. (The cake can be made up to 1 day ahead and left, rolled up, at room temperature.)
8. To make the filling: Stir all of the ingredients except the lemon juice, salt, and pepper together in a bowl until well blended. Taste and add as much juice, salt and pepper as you’d like. (The filling can be refrigerated, covered, overnight.)
9. To assemble the roll-up: Unroll the cake—you can leave it on the towel—and spread the filling evenly over it, leaving just a thin strip bare at the far end. Using the towel and your hands, roll the cake up as neatly and carefully as you can, finishing with the seam on the bottom (or as close to the bottom as you can manage). Slice off—and nibble on—the ragged ends.
10. To finish the roll-up: If you’d like to top the roll-up, toss the cucumber and radish slices with a squirt of lemon juice, season with a little salt and pepper, and arrange in an attractive pattern down the length of the roll. Alternatively, add some arugula to the mix and serve as a salad alongside the roll-up. The roll-up is ready to serve now, or you can refrigerate it and serve chilled—it’s good both ways.
11. To store: The roll-up can be wrapped in plastic and kept in the refrigerator for up to 1 day.