Preheat the oven to 150C. Grease and line the base and sides of a 20cm loose bottom cake tin. Start by heating a pan and cook the pears with the butter for 5 minutes until soft. Next, beat together the ricotta, egg yolks, almond extract and sugar in an electric mixer until smooth. Stir in the almond meal and lime zest. Whisk the egg whites in a clean, dry bowl until soft peaks. Fold 1/3 of the egg whites into the ricotta mixture to loosen, then fold in the remaining. Spread ½ of the mixture into the tin then lay over the pears. Cover with the remaining mixture and flatten out. Bake in the oven for 30 minutes, then sprinkle with the flaked almonds and bake for a further 15 minutes until golden and a skewer comes out clean. Cool slightly, then turn on to a wire rack. Cool completely then dust with icing sugar to serve.