Start by bringing a large pot of salted water to a boil. Add the cauliflower florets and cook for about 5 minutes until they are tender but still firm. Drain them well in a colander and set aside.
In a skillet, heat 3 tablespoons of olive oil over medium heat. Add the chopped red onion and sauté for 5-7 minutes until it becomes soft and translucent. Stir in the finely chopped rosemary and cook for an additional minute. Remove from heat and let it cool slightly.
In a large mixing bowl, whisk together the eggs until they are well combined. Add the chopped basil, remaining olive oil, and a good pinch of salt and black pepper. Mix until everything is incorporated.
In another bowl, whisk together the sifted all-purpose flour, baking powder, ground turmeric, and half of the grated cheese. This will ensure even distribution of the leavening agents and spices.
Gradually add the dry ingredients to the egg mixture, stirring gently until just combined. Then, fold in the sautéed onions and the cooked cauliflower florets. Be careful not to overmix; you want to keep the cauliflower pieces intact.
Preheat your oven to 180°C (350°F). Brush your baking dish with melted unsalted butter, ensuring it's well coated. Pour the cauliflower mixture into the prepared dish, smoothing the top with a spatula.
Sprinkle the remaining grated cheese evenly over the top. Then, sprinkle the white sesame seeds and nigella seeds for a crunchy texture and additional flavor.
Place the baking dish in the preheated oven and bake for 40-45 minutes, or until the top is golden brown and a toothpick inserted into the center comes out clean.
Once baked, remove the cauliflower cake from the oven and let it cool for about 10 minutes before slicing. Serve warm or at room temperature, and enjoy the delightful flavors!
