Preheat oven to 350F. Butter and line a loaf pan with parchment paper with overhang sides for easy removal.
In a medium bowl, whisk together the melted butter, sugar, eggs, sour cream or yogurt, lemon zest, and vanilla extract. Set aside.
½ cup unsalted butter, 1 cup (200g) granulated sugar, ⅓ cup sour cream or plain yogurt, 1 Tbsp lemon zest, 1 tsp vanilla extract, 2 large eggs
In a large bowl, whisk together the flour, baking powder, and salt. Toss in the rhubarb to coat.
1 ¾ cup (220g) all-purpose flour, 1 Tbsp baking powder, ½ tsp kosher salt, 1¾ cups (210g) rhubarb
Add the wet ingredients to the dry ingredients and mix until just combined. Transfer the batter to the prepared pan and spread out evenly. Top with remaining rhubarb and sprinkle with sugar.
¼ cup (30g) rhubarb, 1-2 Tbsp granulated sugar
Bake for 55-65 minutes or until a toothpick inserted into the center comes out clean.
Notes
Leftovers can be in an airtight container at room temperature for up to 3 days. For longer storage, refrigerate the bread in a sealed container for up to 1 week. Allow it to come to room temperature or warm it slightly before serving.