With the rack in the middle position, preheat the oven to 350°F (180°C). Line an 8-inch (20 cm) springform pan with parchment paper. Do not butter.
In a bowl, combine the gluten-free flour, ground almonds and baking powder. Set aside.
In another bowl, beat the egg yolks, egg, oil, milk, vanilla and ¼ cup (55 g) of the sugar with a whisk. Stir in the dry ingredients and mix until smooth. Set aside.
In a third bowl, beat the egg whites with an electric mixer until soft peaks form. Gradually add the remaining sugar and beat until stiff peaks form. Fold half of the meringue at a time into the batter, stirring vigorously (see note). Spread the batter into the prepared pan.
Bake for about 1 hour 10 minutes or until a toothpick inserted into the centre of the cake comes out clean. Let cool completely on a wire rack before unmoulding.
Place the egg whites and vanilla in a large bowl. Set aside.
In a small pot over medium-high heat, bring the sugar and water to a boil. Let simmer until a candy thermometer reads 240°F (116°C). Remove from the heat.
Beat the egg whites and vanilla with an electric mixer on medium speed until frothy. With the machine running, drizzle the hot syrup over the whites, avoiding the mixer’s beaters. Beat until completely cooled and stiff peaks form.
Add the butter, 1 or 2 cubes at a time, beating until smooth and creamy. With a spatula, scrape the bottom of the bowl several times during this step. Set aside.
Run the blade of a knife between the cake and the pan and unmould. Cut the cake horizontally to obtain 2 layers.
Frost the surface of 1 layer with one-third of the buttercream. Cover with the second layer. Apply a crumb coat by covering the entire cake with a thin layer of buttercream. Refrigerate for 20 minutes. Completely frost the cake with the remaining buttercream.
In this recipe, there’s no need to be delicate when stirring the meringue into the batter. The meringue gives the cake its spring while the baking powder helps it rise.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.