Preheat the Oven

Twenty minutes or longer before baking, set an oven rack in the lower third of the oven and preheat the oven to 350°F/175°C.

Combine Half the Sugar, the Flour, and Salt

In a small bowl, whisk together ¾ cup/5.3 ounces/150 grams of the sugar, the flour, and salt until evenly combined. Sift the remaining sugar onto a piece of parchment.

Beat the Egg Whites into a Stiff Meringue

In the bowl of a stand mixer fitted with the whisk beater, beat the egg whites and cream of tartar on medium-low speed until foamy. Gradually raise the speed to medium-high and beat until soft peaks form when the beater is raised. Gradually beat in the remaining sugar and continue beating on medium-high speed until very stiff peaks form when the beater is raised slowly. Beat in the lemon juice and vanilla until combined.

Make the Batter

Sift the flour mixture over the meringue, ¼ cup at a time. With a large balloon whisk, slotted skimmer, or large silicone spatula, fold in the flour mixture quickly but gently. It is not necessary to incorporate every speck until the last addition.

Using a long narrow spatula or silicone spatula, spread a thin layer of batter onto the sides of the pan to ensure smooth sides. Gently scoop the rest of the batter, distributing it evenly into the pan. In a 16 cup pan, it will be ½ inch from the top of the rim. Run a small metal spatula or knife through the batter to prevent air pockets and smooth the surface evenly.

Bake the Cake

Bake for 30 to 40 minutes, or until golden brown, a wire cake tester inserted between the tube and the side comes out clean, and the cake springs back when pressed lightly in the center. (A wooden skewer will still have a few moist crumbs clinging to it.) During baking, the center will rise about 2 inches above the pan, but will sink almost to level with the pan when done. The surface will have deep cracks like a soufflé.

Cool and Unmold the Cake

Immediately invert the pan onto the prepared wire rack or invert the center tube opening of the pan onto the neck of the bottle to suspend it well above the countertop. Cool completely in the pan, about 1½ hours.

To loosen the sides of the cake from the pan, use a rigid sharp knife or stiff metal spatula, preferably with a squared off end. Scrape firmly against the pan’s sides and slowly and carefully circle the pan. In order to ensure that you are scraping against the sides of the pan and removing the crust from the pan, leaving it on the cake, begin by angling the knife or spatula about 20 degrees away from the cake and toward the pan, pushing the cake inward a bit. It is best to use a knife blade that is at least 4 inches long and no wider than 1 inch.

Grasp the center core and lift out the cake. Run a wire cake tester or wooden skewer around the center core. Dislodge the cake from the bottom with a metal spatula or thin sharp knife. Invert the cake onto a flat plate covered with plastic wrap that has been lightly coated with nonstick cooking spray and then reinvert it onto a serving plate. Let the cake sit for 1 hour, or until the top is no longer tacky. Then cover it with a cake dome or wrap it airtight. Wash and dry the tube pan to use for assembling the cake.

Make the Lemon Curd

See recipe.

Whip the Cream

Into a large mixing bowl, pour the cream and refrigerate for at least 15 minutes. (Chill a handheld mixer’s beaters alongside the bowl.)

When the lemon curd has cooled, whip the cream, starting on low speed and gradually raising the speed to medium-high as it thickens, until the cream mounds softly when dropped from a spoon. With a whisk or silicone spatula, fold in the lemon curd until completely incorporated. Cover the bowl tightly with plastic wrap and refrigerate.

Complete the Lemon Mousse Filling

Use a large balloon whisk or silicone spatula to fold the Italian meringue into the lemon cream mixture in three parts.

Prepare the Cake

Place two 3 foot long sheets of parchment on a flat surface. Slice off the crusty top of the cake to make a semiflat surface. Measure down ¾ inch and score the cake with a serrated knife. Using the scored line as a guide, cut through the cake. With two spatulas, lift the cut cake ring off the cake and place it on the parchment.

Invert the cake. Measure down ½ inch and score the cake with a serrated knife. Using the scored line as a guide, cut through the cake. With two spatulas, lift the cut cake ring off the cake and place it on the parchment.

Cut the remaining cake into ¾ inch cubes or tear it into roughly ¾ inch pieces and place them on the second piece of parchment.

Cover the two rings and cubed or torn pieces with plastic wrap. Leave the cubed or torn pieces uncovered if the cake is very moist.

Unmold the Cake

Chill the serving plate. Lightly moisten the plate with water to make it easy to reposition and center the cake.

Run a wire cake tester or wooden skewer around the center core. Heat a dish towel by running it under very hot water and wringing out the excess. Wipe the sides and bottom of the cake pan with the hot towel to help release the cake.

Set the cake pan on top of a canister with a diameter smaller than the removable portion of the pan’s bottom and taller than the pan’s sides, and gently press down on the sides of the pan. If the sides do not slide down easily, apply more heat.

Run a long metal spatula between the bottom of the cake and the pan. Set the serving plate on top and invert the cake onto it.

Serve with raspberry sauce or lightly sweetened whipped cream, if desired.

Make the Italian Meringue

Have ready a 2 cup or larger glass measure with a spout.

Into a 1 cup glass measure with a spout, pour the 3 tablespoons/44 ml of cold water and sprinkle the gelatin over the top. Stir to moisten the gelatin and let it sit for a minimum of 5 minutes. If it will sit longer, cover with plastic wrap to prevent evaporation.

Set the cup in a pan of simmering water for a few minutes, stirring occasionally, until the gelatin is dissolved. It will thicken slightly. Remove the pan from the heat. (This can also be done in a microwave, with 3 second bursts, stirring once or twice until dissolved.)

Pour the egg whites into the bowl of a stand mixer fitted with the whisk beater, or into a large bowl and have ready the handheld mixer. Add the cream of tartar.

In a small heavy saucepan, preferably nonstick, stir together 1 cup/7 ounces/200 grams of the sugar and the ¼ cup plus 2 tablespoons/89 ml of water until the sugar is completely moistened. Heat on medium-high, stirring constantly, until the sugar dissolves and the syrup is bubbling. Stop stirring and reduce the heat to low. (If using an electric range, remove the pan from the heat.)

Beat the egg whites and cream of tartar on medium-low speed until foamy. Raise the speed to medium-high and beat until soft peaks form when the beater is raised. Gradually beat in the remaining ⅓ cup of sugar until stiff peaks form when the beater is raised slowly.

Increase the heat under the sugar syrup to medium-high and continue to boil for a few minutes until an instant-read thermometer reads 248° to 250°F/120°C. Immediately transfer the syrup to the glass measure to stop the cooking.

If using a stand mixer, with the mixer off to keep the syrup from spinning onto the sides of the bowl, add the syrup to the egg whites. Begin by pouring in a small amount. Immediately beat on high speed for 5 seconds. Add the remaining syrup the same way in three parts. For the last addition, use a silicone spatula to remove the syrup clinging to the glass measure and scrape it against the beater. If the syrup has hardened before most of it has been poured, soften it to pouring consistency for a few seconds in the microwave.

If using a handheld mixer, beat the syrup into the egg whites on high speed in a steady stream. Do not let the syrup fall on the beaters or they will spin it onto the sides of the bowl.

Lower the speed to medium, add the gelatin mixture, and beat for 2 minutes. Decrease the speed to low and continue beating until no longer warm to the touch, about 10 minutes, longer if using a handheld mixer.