1. Grease/butter a 22 cm springform pan. Line the bottom with a circle of parchment paper. Preheat oven to 180 degrees C.

2. In a large mixing bowl, combine the egg yolks and sugar. Beat for 3 minutes or until thick, creamy and lightened in colour. Add the almond flour and the orange zest and use a spatula to fold and stir together until incorporated. 

3. In a second large mixing bowl, add 4 egg whites and beat together until stiff peaks form. Fold the egg whites 1 heaped spoonful at a time into the almond batter, folding with each addition just until incorporated and an even consistency.

4. Transfer the batter to the prepared baking pan and sprinkle the top with 1/4 cup sliced almonds. Bake at 350˚F (176˚C) for 30 minutes or until the top is firm.

5. Let the cake rest in the pan for 15 minutes then run a thin spatula around the sides, invert it onto a dish and then place it right side up on the rack. Let it cool to room temperature and garnish with sliced almonds, icing sugar and orange slices if desired.

TIP

*A sweeter glazed topping can be achieved by boiling together 1/2 cup of cream and 2 Tbsp sugar and a little almond essence and pouring it over the cake before adding toasted almonds and orange zest.