Preheat the oven to 350F. Line a 8 or 9-inch cake pan or springform pan with parchment, and grease or spray the sides.
In a large mixing bowl, add the butter and sugar and beat with an electric mixer for a few minutes until creamed and very smooth. Add the ricotta cheese (well drained) and beat some more.
Scrape down the side of the bowl, and add the egg yolks, lemon zest vanilla, and almond extracts. Continue beating on medium speed until very smooth.
Add the salt and the almond flour. Mix until just combined.
Beat the egg whites on medium-high speed until stiff peaks form. Add a third of the whipped egg whites to the cake batter and gently fold. Repeat with remaining egg whites, and fold until incorporated.
Pour the cake batter into the prepared cake pan. Sprinkle the top with the sliced almonds and bake at 350F for 55-60 minutes, until set and golden brown on top. Let the cake cool to room temperature, then carefully remove the outer ring of the pan. Dust with confectioner’s sugar before serving.
