Preheat the oven to 175 degrees Celsius (350 degrees Fahrenheit)
Spray a muffin tray with cooking spray or alternatively generously wipe melted coconut oil over each muffin cup.
In a bowl whisk together the eggs, almond milk, salt, pepper and mustard powder. Add in the cauliflower rice.
Place a spoonful of the ham, red onion and spinach into the bottom of 9 muffin cups. Pour the egg and cauliflower mixture over top of each and then top each muffin with the remaining ham and spinach.
Bake in the oven for 25 minutes until the edges are lightly browned and the tops are fully set.
Run a spatula around each muffin to loosen and then place on a wire rack to cool.