With the rack in the middle position, preheat the oven to 350°F (180°C). Generously butter and flour a 10 to 12-cup (2.5 to 3-litre) Bundt pan.
In a bowl, combine the flour, baking powder, baking soda and salt. Set aside.
In another bowl, beat the egg whites with an electric mixer until frothy. Gradually add 1/2 cup (105 g) of the sugar, beating until soft peaks form. Set the meringue aside.
In a third bowl, cream the butter, the remaining sugar (3/4 cup/160 g) and vanilla with the electric mixer. Add the egg yolks and beat until smooth. At low speed, add the dry ingredients alternately with the buttermilk.
With a spatula, stir a quarter of the meringue into the batter. Gently fold in the remaining meringue. Spoon the batter into the prepared pan.
Bake for 45 minutes or until a toothpick inserted into the centre of the cake comes out clean. Let cool completely on a wire rack. Unmould and place on a serving dish.
In a bowl, combine the icing sugar and milk. Glaze the cake and top with the gumballs.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.