Skillet Lemon Soufflé

1. Adjust oven rack to middle position and heat oven to 375 degrees. Using stand mixer fitted with whisk, whip egg whites and cream of tartar on medium-low speed until foamy, about 1 minute. Increase speed to medium-high and whip whites to soft, billowy mounds, about 1 minute. Gradually add 1⁄3 cup sugar and salt and whip until glossy, stiff peaks form, 2 to 3 minutes. Gently transfer whites to clean bowl; set aside.
2. Using stand mixer fitted with whisk (do not wash bowl), whip egg yolks and remaining 1⁄3 cup sugar on medium-high speed until pale and thick, about 1 minute. Whip in lemon zest, juice, and flour until incorporated, about 30 seconds.
3. Fold one-quarter of whipped egg whites into yolk mixture until almost no white streaks remain. Gently fold in remaining egg whites until just incorporated.
4. Melt butter in 10-inch ovensafe skillet over medium-low heat. Swirl pan to coat it evenly with butter, then gently scrape soufflé batter into skillet and cook until edges begin to set and bubble slightly, about 2 minutes.
5. Transfer skillet to oven and bake soufflé until puffed, center jiggles slightly when shaken, and surface is golden, 7 to 11 minutes. Using potholder (skillet handle will be hot), remove skillet from oven. Dust soufflé with confectioners’ sugar and serve immediately.

Do not open the oven door during the first 7 minutes of baking, but do check the soufflé regularly for doneness during the final few minutes in the oven. Be ready to serve the soufflé immediately after removing it from the oven. Using a 10-inch traditional (not nonstick) skillet is essential to getting the right texture and height in the soufflé.

SKILLET CHOCOLATE-ORANGE SOUFFLÉ
Grating the chocolate fine is key here; we find it easiest to use either a rasp-style grater or the fine holes of a box grater.
Substitute 1 tablespoon grated orange zest for lemon zest and 1⁄3 cup orange juice for lemon juice. Gently fold 1 ounce finely grated bittersweet chocolate into soufflé batter after incorporating all whites in step 3.