With the rack in the middle position, preheat the oven to 350°F (180°C). Generously butter and flour a 10 to 12-cup (2.5-3 litre) Bundt pan.
In a bowl, combine the flour, baking powder, baking soda and salt. Set aside.
In another bowl, beat the egg whites at high speed with an electric mixer until frothy. While beating, gradually add ½ cup (105 g) of the sugar. Beat until soft peaks form. Set the meringue aside.
In a third bowl, cream the butter, the remaining sugar (1 cup/210 g) and the vanilla with an electric mixer until light and fluffy, about 2 minutes. Add the egg yolks and beat until smooth. At low speed, add the dry ingredients alternately with the buttermilk, beating just until just smooth.
With a spatula, stir about a quarter of the meringue into the batter. Gently fold in the remaining meringue. Spread the batter into the pan.
Bake for 45 to 50 minutes or until a toothpick inserted in the centre of the cake comes out clean. Let cool for 15 minutes. Unmould and let cool completely on a wire rack.