1. Cut rhubarb into 1/2" pieces and set aside.
2. In a large mixing bowl, combine flour, baking powder, baking soda, salt and sugar. Mix well to combine
3. Add in chopped rhubarb and mix just to combine.
4, In a small mixing bowl, lightly beat egg.
5. Add melted butter and orange juice; mix to combine.
6. Add wet ingredients to dry ingredients and stir just until combined.
7. Turn into greased 9 x 5-inch loaf pan.
8. Sprinkle top with brown sugar.
9. Bake in 350F oven for 50 to 60 minutes or until tester inserted in centre comes out clean.
10. Cool in pan for 10 minutes.
11. Turn out onto wire cooling rack and cool for 30 minutes before slicing.