Preheat oven to 185 degrees C (165 degrees fan forced). Heat olive oil in a large frying pan over medium heat. Add onions, garlic and rosemary and cook for 8-10 minutes or until onion is soft. Thinly slice zucchinis and add to pan. Cook 3 minutes. Add potatoes, season with salt and pepper and stir.
Transfer mixture to a bowl, add eggs and parmesan and mix well. Grease a 25cm cake tin and line with baking paper. Arrange zucchini flowers in the base, then pour egg mixture into tin. Smooth top and tap cake tin on work surface to remove air bubbles.
Bake 20-30 minutes or until cooked through and slightly puffy. Set aside for 10 minutes, then turn out onto a plate so the flowers are on top.