Preheat the oven to 400F.
Melt the butter and olive oil in a medium skillet over medium heat. Add the onions and cook for about 6 minutes or until golden brown. Add the garlic and cook for 2 minutes more, stirring occasionally.
Place the cooked onion and garlic in a medium bowl, add the heavy cream, eggs, flour, asparagus, cheddar cheese, parmesan cheese and mix well. Season with salt and pepper.
In a small bowl mix the bread crumbs, parmesan cheese and oregano and set aside.
Pour the mixture into a greased individual oven proof dish. Top with the sliced tomatoes, sprinkle with bread crumbs mixture and bake for about 30 minutes or until set.