Preheat oven to 275°F (135°C). Line two baking sheets with parchment paper and trace three 8-inch circles. Flip the parchment so the marks are on the bottom.

In a clean stand mixer bowl, beat egg whites on medium speed until foamy. Slowly add the granulated sugar, then increase speed to high and beat until stiff, glossy peaks form.

In a separate bowl, whisk together almond flour and powdered sugar. Gently fold the dry mixture into the meringue in three additions, being careful not to deflate the whites.

Transfer meringue to a piping bag and pipe into the traced circles. Bake for 60-75 minutes until firm and pale. Turn off the oven and let the discs cool completely inside with the door slightly ajar.

Whisk egg yolks in a stand mixer until pale. Boil 3/4 cup sugar and 1/4 cup water in a saucepan until it reaches 240°F (115°C). With the mixer on low, slowly stream the hot syrup into the yolks. Whip on high until cooled.

With the mixer on medium-low, add the softened butter one tablespoon at a time. Once all butter is incorporated, mix in the vanilla extract until the buttercream is smooth.

To assemble, place one meringue disc on a serving plate. Spread a layer of buttercream over it. Repeat with the remaining discs and buttercream. Garnish as desired.