Parmesan-Rosemary Cauliflower "Cake"

When I saw this beauty at Annie's site https://www.ciaochowbambina.com/cauliflower-cake/ I knew I had to make it, but change it to a low carb-keto version. The challenge was on. My worries were that it might crumble apart or be dry from the low carb/keto gluten free flours I'd have to use in place of the all-purpose flour Annie used.
It looked gorgeous coming out of the oven. The moment of truth was about to happen. I held my breath when I cut it, fearing for the crumbling or dryness I had worried about...Instead of the heavy sigh I anticipated, I squealed with delight when it sliced beautifully and tasted amazing.
My taste-testers aka family were just as happy with it as I was and asked for large slices! Besides being a great side dish for dinner, it would be wonderful made the day before and served for a party as it reheats beautifully too.
Parmesan-Rosemary Cauliflower "Cake" 2 lb. raw cauliflower florets, coarsely chopped 1 small red onion 1 tbsp. olive oil 1 tsp. dried rosemary leaves, broken 6 eggs 1/2 cup scooped almond flour (I use this brand) 5 tbsp. golden flax meal (I use this brand) 2 tbsp. coconut flour (I use this brand) 1-1/2 tsp. baking powder (gluten free) non-GMO (grain free if needed) (I use this brand) 1 cup shredded aged Parmesan cheese or other sharp cheese 2 tsp. unrefined sea salt (I use this brand) 1/2 tsp. ground black pepper or to taste 2 cups baby spinach leaves ( slightly packed) 1. Preheat the oven to 400 F. Line the base and sides of a 9 inch springform cake pan with parchment paper. Place cauliflower in a large saucepan of salted water; bring to a simmer. Simmer for about 15 minutes until florets are quite soft; drain thoroughly in a colander, Set aside. 2. Cut three 1/4-inch thick round slices off one end of the red onion and set aside. Coarsely chop remaining onion to measure 2/3 cup, place in a small skillet with olive oil and rosemary. cook over med-low heat until softened, about 7 minutes. Remove from heat and set aside to cool. 3. In a large bowl, beat eggs with wire whisk. Add almond flour, ground flax, coconut flour, baking powder, 1 teaspoon salt and pepper; whisk thoroughly. Stir in Parmesan. Gently stir in cauliflower and spinach. Pour the cauliflower mixture into the pan, spreading it evenly. Separate onion into smaller rings and arrange on top. Place in the center of the oven and bake for 45 minutes, until golden brown and set. Remove from the oven and let rest for about 15 minutes before serving. Cut into 10 wedges to serve. Cover and store leftovers in the refrigerator. This reheats well. Servings: 12 Nutrition Facts Serving size: 1/12 of a recipe (4.5 ounces). Nutrition information calculated from recipe ingredients. Amount Per Serving Calories 141.12 Total Fat 9.29g Saturated Fat 2.66g Cholesterol 97.8mg Sodium 536.51mg 22 Potassium 297.07mg Total Carbohydrates 7.39g Fiber 3.43g Sugar 1.95g Protein 9.12g