Preheat your oven to 350°F (175°C) and steam the cauliflower until tender (about 8-10 minutes). Pulse in a food processor until it resembles rice.

Sauté fresh spinach in a skillet over medium heat for 2-3 minutes until wilted. Combine riced cauliflower, spinach, cream cheese, cheddar cheese, and eggs in a bowl. Stir until creamy.

Grease a 9x13 inch baking dish with olive oil. Pour the mixture into the dish and spread evenly. Optionally, sprinkle additional cheddar cheese on top.

Bake for 30-35 minutes, until the top is golden brown and edges are slightly crisp. The center should jiggle slightly but be firm.

Cool the casserole for 5-10 minutes on a wire rack, then serve warm, garnished with fresh herbs if desired.