Cooking oil spray, to grease
1 large whole watermelon
250g almond meal
1 tsp baking powder
1 tsp ground cinnamon
½ tsp ground cardamom
½ tsp fine salt
¾ cup honey
75g unsalted butter, melted
2 x 125g punnets raspberries
1 cup pistachios, roughly chopped
1 cup caster sugar
450ml thickened cream
1 tsp vanilla bean paste
Note: Allow 2 hours cooling
Preheat oven to 160°C. Grease two 22cm round cake tins with cooking oil spray and line bases and sides with baking paper. Using a large sharp knife, cut a 1.5cm-thick disc of watermelon from the centre of the melon, then remove skin. Set aside remaining watermelon.
Put another 22cm round cake tin on top of watermelon slice and cut around edge using a small sharp knife. Pat watermelon slice dry using paper towel, then set aside. Roughly chop 3 cups of the remaining watermelon, then press through a fine sieve over a large bowl to catch juice. (You will need 1 cup of juice.)
Combine almond meal, baking powder, spices and salt in a large bowl, then add eggs, honey and butter. Stir until smooth, then fold in 1 punnet of the raspberries. Divide mixture between prepared tins, scatter with ½ of the pistachio, then bake for 20-25 minutes or until just firm. Do not remove from tins.
Meanwhile, pour watermelon juice and ½ cup of the caster sugar into a small saucepan. Put over a high heat and bring to the boil, then cook for 10 minutes or until syrupy. Brush syrup over warm cakes in tins, then set aside for 2 hours to cool completely.
Put cream, vanilla and remaining sugar in a large bowl and beat, using an electric hand mixer, until stiff peaks form. Put 1 cake on a serving plate or cake stand and spread with ½ of the cream. Put watermelon slice on top of cream, then add second cake on top of watermelon. Dollop with a little of the remaining cream.
Decorate top of cake with remaining raspberries and pistachio, then serve with remaining cream on the side.