Preheat your oven to 350°F / 175°C. Lightly grease an 11x8-inch or similar-sized oval baking dish.
In a medium skillet over medium heat, melt the butter.
Add the chopped onions and sauté until they become soft and translucent, about 3-4 minutes.
Reduce the heat to low.
Pour in the heavy cream, salt, and pepper, stirring to combine.
Let it simmer gently for 2 minutes to slightly thicken.
Remove the skillet from the heat and stir in the frozen riced cauliflower and shredded cheddar cheese until everything is well-coated and the cheese begins to melt.
Spread the mixture evenly into your prepared baking dish.
Bake for 25 minutes, or until the edges are bubbly and starting to brown.
While the casserole bakes, mix the crushed pork rinds and grated Parmesan cheese in a small bowl.
After 25 minutes, remove the casserole from the oven, sprinkle the topping evenly over the surface, and return it to the oven for 5-8 more minutes, until the topping is golden brown and crisp.
Let rest for a few minutes before serving.
