Cauliflower Cake

Name: Cauliflower Cake
Ingredients: 1 small cauliflower, outer leaves removed, broken into 1 1/4-inch/3-cm florets (1 pound/450 g); 1 medium red onion, peeled (6 ounce/170 g); 5 tablespoons/75 ml olive oil; 1/2 teaspoon finely chopped rosemary; 7 eggs (scant 1 pound/440 g); 1/2 cup/15 g basil leaves, chopped; 1 cup/120 g all-purpose flour, sifted; 1 1/2 teaspoons baking powder; 1/3 teaspoon ground turmeric; 5 ounces/150 g coarsely grated Parmesan or another mature cheese; Salt and black pepper; Melted unsalted butter, for brushing; 1 tablespoon white sesame seeds; 1 teaspoon nigella seeds