• Grease an 8-inch (20cm) deep, round cake pan & line base & side with parchment paper. Preheat oven to 325°F (160°C/gas mark 3).
• Beat butter, 1/3 cup of sugar, vanilla & orange rind in a large bowl of electric mixer for 7 to 10 minutes, scraping the side of the bowl down a couple of times during beating, until light & creamy. Add the yolks & beat 2 to 3 minutes until well combined & mixture is slightly fluffy.
• Add ground almonds & ricotta & beat until well combined.
• Using a clean, dry balloon whisk attachment, beat egg whites in a clean, medium-size bowl, using an electric mixer, until stiff peaks form. Gradually add the remaining sugar & beat until thick & glossy.
• Fold one-third of the egg white mixture into the almond mixture. Add the remaining egg white mixture, making sure to gently fold the mixture until combined. Spoon mixture into cake pan; smooth top. Sprinkle with slivered almonds. Bake for 55 to 60 minutes or until cake is a light golden-brown color & a skewer comes out clean when inserted into the center of the cake. Place cake, in the pan, on a wire rack & let the cake cool completely before turning onto a serving platter. The cake may dip in the center as it cools. The cake can be kept at room temperature for a day or stored, covered in the fridge. Serve the cake cold or at room temperature.
• Just before serving, dust cake with icing sugar. Serve with dried orange slices, cream & sauce. Serves 6 to 8.

To make the Orange Butter Sauce:

• Combine juice & sugar in a small saucepan. Bring to a boil, let boil for 5 minutes to thicken a little. Whisk in butter 1 tablespoon at a time, whisking constantly & waiting until butter has melted before adding another tablespoon. Serve sauce warm with the cake.