Preheat an oven. Line a cake pan or springform pan with parchment.
Place softened butter, granulated sugar, vanilla extract, and almond extract into the bowl of a stand mixer fitted with paddle attachment.
Add the egg yolks. Add the ricotta cheese and lemon zest, then continue beating. Pour in the almond flour. Mix until just combined.
Beat the egg whites on medium-high speed until stiff peaks form. Gently fold half of the egg whites into the cake batter.
Pour the cake batter into the greased cake pan. Sprinkle the sliced almonds evenly over the top of the cake, then bake.
Allow the cake to cool. Dust with confectioner’s sugar, then slice and serve warm or at room temperature.