Preheat the oven to 350F.

In a large skillet, warm the olive oil over medium heat. Add the beef, onion, garlic, celery and ½ teaspoon salt. Cook until the meat is browned, about 5-7 minutes. Stir in the tomatoes and remove from heat. Transfer to a 9x9 inch baking dish.

Steam the cauliflower until it becomes soft. Allow it to cool for 10 minutes so that the steam evaporates excess water. Add to a food processor or high-speed blender with the heavy cream, ¼ cup shredded cheddar, oregano and remaining ½ teaspoon salt. Puree until smooth.

Spread the cauliflower mixture on top of the beef in an even layer. Top with remaining ½ cup cheddar cheese.

Bake for 40 minutes, or until cheese is melted and slightly golden on top.

Store leftovers, covered, in the fridge.