Preheat oven to 325℉ and spray a 12 x 17 inch sided cookie sheet with cooking spray. (Or a sided cookie sheet within a few inches of those dimensions.)
Line the cookie sheet with a sheet of parchment paper. Press and smooth the parchment onto the bottom and the sides of the pan. See Note #3 below
In a medium bowl sift together cake flour, baking powder and salt. Stir well.
In a large bowl combine egg yolks and sugar. Using a hand held mixer beat until the sugar has dissolved, the yolks turn a pale yellow color and the mixture increases in volume, about 2-3 minutes. See Note #4 below
Working in increments, slowly add the oil and beat until fully incorporated.
Pour in milk and beat until well combined. Add in lemon zest and extract and beat until well combined.
Add half of the flour mixture and beat on medium speed until just combined. Repeat with second half of flour mixture and beat until the batter is just free of lumps but no longer.
Meringue for Cake Batter
Place the eggs white into a clean and dry bowl of a stand mixture. Sprinkle cream of tartar over egg whites.
Using whisk attachment whip on high speed until the whites are frothy. Add sugar slowly at this point while continuing to whip until stiff peaks form, about 4-6 minutes. See Note #5 below
Gently fold 1/3 of meringue mixture into cake batter making sure to not over mix. Repeat two more times with the remaining egg whites. See Note #6 below
Baking the Cake
Pour batter into prepared cookie sheet and spread evenly with a bowl scrapper.
Give the pan a tap on a flat countertop to release any air pockets. Bake on the middle rack until the top turns golden brown and the top of the cake springs back when touched, approximately 20-22 minutes. See Note #7 below
First Rolling of the Cake (while still hot)
Lay a clean kitchen towel on a flat countertop and using hot pads immediately flip the cookie sheet over onto the kitchen towel.
Carefully peel the parchment off of the cake (the cake will be hot). Lay another clean kitchen cloth over the top of the cake.
Starting on the short side of the cake, roll the hot cake between the two towels.
Allow the cake to cool completely either at room temperature or in the refrigerator before adding the filling.
Lemon Curd Whipped Cream
Add the heavy whipping cream and lemon extract to a chilled bowl. Whip the cream using an immersion blender or hand held mixer on medium high speed until stiff peaks form making sure to stop halfway to scrape down side of bowl. See Note #8 below
Once the cream is fully whipped fold in 1/2 cup chilled lemon curd. Refrigerate until needed.
Filling the Cake and Second Rolling
Unroll the cake onto a flat surface once it is completely cooled.
Add 2/3 of the prepared whipped cream to the top of the cake and spread evenly leaving approximately 1/2 inch unfrosted around the edges.
Starting with the edge that has the tightest curl, roll the cake.
Transfer the rolled cake onto a platter making sure the seam side faces down.
Frosting the Cake
With the remaining 1/3 of prepared whipped cream, frost the cake.
Add the 4 tablespoons of lemon curd evenly to the top of the cake in 4 dollops.
Using a spoon make circular motions partially blending the curd into the whipped cream.
Refrigerate until ready to serve.
Recipe NotesNote #1- If using Maldon's Sea Salt for its low iodine levels grind it in a mortar and pestle before adding to the dry ingredients.Note #2- Here is a helpful video on how to separate eggs. Note #3- Spraying the pan with cooking spray keeps the parchment in place on the cookie sheet. It is ok that the parchment overlaps the sides of the pan. Lining the pan makes for an easy release once the cake is baked.Note #4- Using a hand held mixer for the cake batter and a stand mixer for the meringue makes for fast and efficient cake preparation. Also, the stand mixer has enough power to reach high speeds ideal for making meringue. Note #5- Stiff peaks are formed when the whisk is turned right side up and the peaks stands tall without moving. Note #6- Once mixed there should be no streaks of white from the meringue in the batter. To avoid over mixing fold just until the white disappears. Note #7- Larger cookie sheets will cause the cake to bake a few minutes faster. It is best to keep a close eye on the cake at around the 16 minute marker of baking. Note #8- The container used for the whipped cream seen in the images above is part of the immersion blender set.