Preheat oven to 350°F (175°C). Grease a 9x5-inch loaf pan and line with parchment if desired. Toss chopped rhubarb with 1 tablespoon flour to prevent sinking.
Whisk together flour, baking powder, baking soda, salt, and cinnamon (if using) in a medium bowl.
In a large bowl, combine sugar and eggs until blended. Add oil, yogurt, and vanilla; stir until smooth.
Gently fold dry ingredients into wet until just combined. Fold in rhubarb and nuts with a light hand to avoid overmixing.
Pour batter into prepared pan and smooth the top. Bake 50–60 minutes, or until a toothpick comes out with a few moist crumbs. Tent with foil if top browns too quickly.
Cool in pan 10–15 minutes, then transfer to a wire rack. For the glaze, whisk powdered sugar with milk and vanilla to desired consistency and drizzle over cooled loaf.
Notes
If using frozen rhubarb, thaw and drain well to avoid excess moisture.
Swap 1/2 cup flour for whole wheat for a nuttier flavor and chewier texture.
Store at room temperature for up to 2 days, refrigerate up to a week, or freeze slices for longer storage.