Strawberry and watermelon cake

Name: Strawberry and watermelon cake
Prep time: 45 min
Cook time: 15 min
Total time: 1 h
Cuisine: European
Ingredients: 250 gm seedless watermelon, thinly sliced; 60 ml rosewater (¼ cup); 4 tbsp caster sugar; 40 gm almond meal; 500 gm strawberries (about 2 punnets), halved; 10 seedless red grapes, halved; 1 tbsp slivered pistachios (see note); 1 tbsp dried rose petals (see note); 150 gm almonds, coarsely chopped; 150 gm pure icing sugar, sieved; 5 eggwhites; 135 gm caster sugar; 300 ml thickened cream; 30 gm caster sugar; 2 tbsp rosewater