Saute the onions and mince in the oil. Add the washed rice.
Cook until the rice turns clear. Season with salt and black pepper. Add the finely chopped spearmint.
Let the stuffing cool and fill the peppers with it. Arrange them in a suitable oven dish.
Pour in warm water to cover the peppers halfway up.
Bake in a preheated oven. Flip the peppers over halfway through baking.