Preheat oven to 350°F (177°C). Lightly grease and line the bottom and sides of a 9 x 13-inch baking pan with parchment paper. Do not grease the paper. Ensure the longer sides have approximately 1–2 inches of parchment paper overhang to make unmoulding easier.
In a bowl, whisk together the cake flour, cornstarch, baking powder, salt, and baking soda until free of lumps.
In a large bowl, using a hand mixer or a large whisk, beat together the egg yolks, the Redpath® Golden Yellow Sugar, canola oil, milk, and vanilla extract, until sugar is dissolved and egg yolk mixture is thickened and pale in colour; 3 minutes.
Sift the dry ingredients evenly over the surface of the yolk mixture. With a large rubber spatula, gently fold in until no flour streaks remain; do not overmix. Set aside.
Add egg whites to the bowl of a stand mixer fitted with the whisk attachment or a large bowl using a hand mixer. Whisk on medium speed until foamy. Add in lemon juice, and continue whisking until egg whites are opaque and white and the “bubbles” of the egg whites are small and uniform. Gradually add the Redpath® Granulated Sugar in a slow but steady stream.
Once all the sugar is added, increase speed to medium-high and whip to a stiff peak; whites should be thick and glossy. To test, lift the whisk from the meringue; it should hold a peak with no droopy tip; be careful not to over-whip.
Add and quickly fold in ⅓ of the egg whites to the yolk mixture; this will lighten the yolk mixture, making it easier to fold in the remaining egg whites. Add remaining whites to the yolk mixture. Quickly and gently fold in until no egg white streaks remain and batter is smooth.
Pour and spread the batter into the prepared pan with an offset spatula, ensuring an even thickness. Drop the pan a few times onto a flat work surface to rid batter of any large air pockets. Place pan into the preheated oven. Bake until top is golden in colour and not sticky to the touch; 18 to 22 minutes or until a skewer inserted into the center comes out clean, or when the sponge is gently pressed, it slowly springs back.
Remove cake from oven and let cool slightly in the pan; 3 to 5 minutes. Place a wire cooling rack over the pan and carefully flip the cake onto the cooling rack. Carefully peel away the parchment paper.
Immediately place a piece of parchment paper onto the cake’s surface, place another wire cooling rack (larger than the cake) onto the parchment paper and flip the cake right side up. Cool completely; 2 hours.