Preheat oven to 180°C and grease a cake tin.
Beat the egg white with a pinch of salt until stiff peaks are formed and set aside.
Beat eggs, sweetener, oil and vanilla extract.
Add spelt flour and baking powder and mix well.
Gently fold in egg whites.
Pour batter into prepared cake tin. You can use a bundt tin, spread the batter on a rimmed baking sheet for a layer cake of make cupcakes.
Bake until a tooth pick inserted in the middle comes out clean. On a baking sheet, the baking time was 12 minutes, in the bundt tin it took 25 minutes.
Let cool completely before serving.
*Tagatesse is a sweetener twice as sweet as regular white sugar. It can be swapped for sugar or other sweeteners, but keep that ration in mind.