Heat the oven to 180C. Break the cauliflower into medium florets, put them in a pot with a teaspoon of salt, cover with water and simmer for 15 minutes, until quite soft. Strain, and leave in the colander for a few minutes to get rid of all the water.

While the cauliflower's cooking, prepare the batter. Cut a few 0.5cm rings off one end of the onion and set aside (these will go on top of the cake); coarsely chop the rest.

Heat the oil in a pan and on a low heat sauté the chopped onion and rosemary for approx. 8 minutes. Remove from the heat, leave to cool down. Then add the eggs. Whisk to combine.

Place the flour, baking powder and turmeric into a large bowl, and add the parmesan. Add 1.5 teaspoons of salt and plenty of black pepper.

Add the egg mix and whisk to eliminate lumps. Add the cauliflower and stir gently, trying to keep some florets whole.

Use baking paper to line the bottom of a 24cm round cake tin with a removable base. Brush the sides of the tin with butter or spray with olive oil spray. Add in the nigella seeds or sesame seeds and toss them around so they stick to the sides. Tip in the cauliflower mix and arrange the onion rings on top.

Bake the cake in the centre of the oven for 45 minutes or until golden brown and set. Serve just warm or at room temperature.