Prepare the Cauliflower: Preheat your oven to 350°F (175°C). Add the cauliflower florets and cook for about 10 minutes, or until the cauliflower is tender but not mushy.

Sauté the Onion: In a small skillet, heat 1 tablespoon of basil olive oil (or regular olive oil) over medium heat. Add the diced red onion and chopped rosemary. Sauté for about 5-7 minutes until the onion is soft and slightly caramelized. Remove from heat and let cool.

Prepare the Batter: In a large mixing bowl, whisk together the eggs until well combined. Add the chopped sweet basil leaves, sifted flour, baking powder, and grated Pecorino Romano cheese. Blend thoroughly until the batter is silky and lump-free. Adjust seasoning with salt and freshly cracked black pepper according to your taste.

Combine Cauliflower and Batter: Gently fold the cooked cauliflower florets and sautéed onion mixture into the batter, making sure the cauliflower is evenly distributed.

Prepare the Pan: Brush a 9-inch (23 cm) springform pan with melted butter, ensuring the sides and bottom are well-coated. Sprinkle the white and black sesame seeds evenly over the bottom and sides of the pan to create a decorative and flavorful crust.

Bake the Cake: Pour the cauliflower batter into the prepared pan, spreading it evenly. Drizzle the remaining basil olive oil over the top. Bake in the preheated oven for 35-40 minutes, or until the cake is golden brown and a skewer inserted into the center comes out clean.

Cool and Serve: Remove the cake from the oven and let it cool in the pan for about 10 minutes. Carefully release the springform and transfer the cake to a serving plate. Serve warm or at room temperature, garnished with additional fresh basil leaves if desired.