Method
1. Pre-heat oven - 160°C
2. Combine the flour, baking soda, and salt. Set aside
3. In a stand mixer with the paddle attachment, beat the butter, sugar, and 1.5 tsp orange zest together until light and fluffy
4. Add the eggs, one at a time, scraping down the sides of the bowl as needed
5. Add vanilla extract, orange juice and sour cream to the stand mixer bowl
6. Mix until smooth
7. In two batches, add the flour to the wet mixture, mixing until just incorporated
8. Add rhubarb and water to a clean saucepan
9. Cook until soft - medium heat
10. Drain off excess water, and blend into as smooth a sauce as you can
11. Add brown sugar to the purée and mix together
12. Set 1/4 cup of the pureed rhubarb aside for later
13. Prepare an 8″ loaf pan with butter and parchment paper
14. Fill the loaf pan halfway up with cake batter, then pour about 1/3 cup of the rhubarb puree on top
15. Pour the rest of the batter on top of the puree, and use a butter knife to swirl everything together
16. Bake - 1 hr 10 min, 160°C
17. Transfer onto cooling rack and let cool
18. Mix the remaining rhubarb puree with the powdered sugar and remaining orange zest
19. Pour over the loaf and allow to set before serving