Preheat oven to 180°C. Grease and line a 20cm x 30cm baking dish with baking paper.
In a frying pan, heat oil over medium heat. Add onion, garlic and chorizo and cook, stirring regularly, for 3–5 minutes until onion is soft and translucent. Remove pan from heat then stir in seasoning and cayenne. Set aside.
Place cauliflower in a food processor and pulse until a rice-like texture. Transfer cauliflower to a clean tea towel and gently squeeze out excess water. Set aside.
In a large bowl, whisk eggs together then stir in parmesan and spinach. Add onion mix and cauliflower rice and stir to combine. Season with salt and pepper then pour into prepared baking dish. Bake for 20–25 minutes until lightly golden.
Remove slice from oven and allow to cool before turning out onto a flat surface. Cut in circles (squares or triangles!) with an appropriate-sized cutter.
Reheat prior to serving in a lightly oiled pan.