Remove the stems from the green peppers, remove the seeds and cut into fine strips. Peel the onion, chop finely. Melt butter in a large pot. Fry onion in it until golden brown. Add the bell pepper strips and steam covered. In the meantime, wash the tomatoes, remove the stalk and cut into slices. After 15 min add the tomatoes, season with a good pinch of salt. Add 1/8 l of water, cover and let it steam for another 15 min. Wash the rice in cold water, drain and mix with the vegetables. Add the paprika and let it steam, stirring several times, until the rice is completely soft. If necessary, add a little water. Season with salt just before serving.