Preheat the oven to 350 degrees F. Prepare a 9x5 loaf pan (1.5 pound) by greasing and lining it with parchment paper for easy removal. Set aside. In a large mixing bowl, add the all-purpose flour, sugar, baking powder and salt. Whisk until thoroughly combined.
210 grams all-purpose flour, 200 grams sugar, 8 grams baking powder, 3 grams salt
In a separate bowl, add the milk, egg, vanilla extract, sourdough discard, and oil. Whisk until smooth.
120 grams milk, 1 large egg, 8 grams vanilla extract, 100 grams neutral oil, 240 grams sourdough discard, see notes
Pour the wet ingredients into the dry ingredients and mix until just combined. Lastly, fold the pieces of rhubarb into the batter.
240 grams rhubarb, 1/2-inch slices
Pour the quick bread batter into the loaf pan. Finally, sprinkle extra sugar on top of the batter (about 1-2 T).
Bake for 60-65 minutes, or until a toothpick put in the center comes out clean or with a few moist crumbs.
Place on a wire rack to cool slightly before slicing. Enjoy!