Preheat the oven to 350 °F. Butter an 8-inch springform pan and line the bottom only with parchment paper. Set aside
In a bowl, combine flour, baking powder, and salt.
In a separate bowl, beat the egg whites and cream of tartar with mixer until soft peaks form. Gradually add 1/2 cup of the sugar, beating until stiff peaks form.
In a third bowl, beat the remaining sugar, butter, egg yolks, and Vanilla Bourbon flavour with mixer at low speed. Slowly adding in dry ingredients and milk alternating between the two.
Stir a quarter of the meringue into the batter to lighten it. With a spatula, gently fold in the remaining meringue. Pour into the prepared pan.
Bake for approx. 55 minutes or until a toothpick inserted in the centre come out clean. Unmould immediately and let cool on a wire rack (approximately 25mins)