Preheat the oven to 400 degrees.

Prepare a 9 1/2-inch springform pan by brushing it lightly with butter, then lining the bottom and sides with parchment paper. Brush the top of all the parchment paper with butter. Sprinkle in the sesame seeds over bottom and sides, tilting the pan so that they are evenly spread.

Place the cauliflower florets in a saucepan. Pour in water to cover and 1 teaspoon salt. Bring to a boil, then reduce the heat to simmer. Cover and simmer the florets for 15 minutes, or until they yield to pressure when pressed with a spoon (they should be pretty soft).

Drain florets in colander, leaving them to dry and cool off.

Cut 3-4 slices that are 1/4-inch thick from the top side of the red onion. Set aside. Coarsely chop the remaining onion.

Heat the olive oil over medium heat in a medium pot (I used the one I cooked the cauliflower in). Add the chopped onion and rosemary to the oil and cook until soft, stirring occasionally, about 10 minutes.

Remove the onion mixture from the heat to a small bowl and allow to cool.

Mix together flour, baking powder, turmeric, 1 teaspoon salt, and 3/4 teaspoon black pepper in different small bowl.

Place eggs, chopped basil, and cooled onion mixture in large bowl and whisk to blend well.

Add flour mixture to eggs a bit at a time, whisking well to incorporate it all. Add the Parmesan cheese to the egg mixture and blend well.

Fold in the cauliflower florets gently, trying to keep from breaking them up.

Transfer the cauliflower-egg mixture to the prepared pan and spread it as evenly as possible. Top with reserved, separated onion rings.

Place on center rack of the oven and bake for 45 minutes, or until it is golden brown on top and set. You can test it by inserting a knife into the center; it should come out clean.