Heat 1 tablespoon of oil in a large skillet over medium heat. Sauté 1 chopped onion until soft and translucent, about 5 minutes. Add 500g ground beef and cook until browned, approximately 6-8 minutes. Stir in 1 cup cooked rice, 1 cup tomato sauce, and 1 tablespoon oregano. Season with salt and pepper. Simmer for 10 minutes.

Preheat your oven to 180°C (350°F).

Brush the bottom of your baking dish with melted butter or oil. Lay down 5 sheets of phyllo dough, brushing each with butter or oil. Keep unused phyllo covered.

Spoon the beef and rice filling evenly over the phyllo.

Cover the filling with another 5 layers of phyllo, brushing each layer with butter or oil. Tuck the edges of the phyllo down into the baking dish.

Bake for 40-45 minutes until golden and crispy.

Allow to cool for about 10 minutes before slicing and serving.