RASPBERRY, HAZELNUT & RICOTTA CAKE

100g blanched hazelnuts Vegetable oil or butter, for greasing • 200g caster sugar • 175g Essential Plain Flour • 2 tsp baking powder • ½ tsp salt • 3 Essential Free Range White Eggs • 250g pack Essential Italian Ricotta • 1 tsp vanilla extract • 1 unwaxed lemon, zest, plus juice of ½ • 240g pack No.1 Speciality Raspberries • 100g icing sugar Double cream, whipped, to serve (optional)