Make the cake:

Cup of Yum
1. Preheat oven to 350°F/177°C.
2. Line a 8″ by 4″ loaf pan with parchment paper.
3. In a clean stand mixer bowl fitted with a whisk attachment, add in the egg whites and beat until foamy.
4. Add in the cream of tartar (or lemon juice) and continue beating until more bubbles appear.
5. Gradually add in the ¼ C of sugar and whip until the meringue reaches stiff peaks.
6. Transfer the whipped egg whites into a large clean bowl. Set aside.
7. In the same mixing bowl, change to a paddle attachment and add in the butter and sugar.
8. Cream until light and fluffy, about 2-3 minutes.
9. Gradually add in the egg yolks one by one, and then add the milk and lemon oil/lemon juice. Mix until combined.
10. Note: it's OK if the mixture appears curdled.
11. To the egg yolk mixture, sift in about ⅓rd of the dry ingredients (flour, cornstarch, and baking powder) and alternate with ⅓rd of the egg white mixture, repeating until everything is combined together. Be sure not to overmix the batter or the cake will not rise.
12. Transfer the cake batter to the lined loaf pan. Tap the pan to release any trapped air bubbles.
13. Bake at 350°F/177°C for 60-65 mins, until golden brown on top, or until a toothpick inserted comes out clean.
14. Let cake cool completely before icing.

Make the icing:

1. In a bowl, combine the powdered sugar, lavender oil and stir. Add in 1-2 tablespoon of milk, until the icing reaches the desired consistency.
2. Mix in purple sweet potato powder or food colouring if you choose to.
3. Spread over the top of the cake with an offset spatula.
4. Let the glaze set before slicing.
5. Sliced cake can be individually wrapped in plastic wrap and frozen for up to 2 months.
6. Remove from the freezer about 15-20 minutes and leave at room temperature before serving.