Preheat the oven to 350°F (175°C). Grease and flour a 9×5-inch loaf pan or line it with parchment paper.

In a medium bowl, whisk together flour, baking powder, baking soda, and salt. Set aside.

In a large mixing bowl, cream the softened butter and sugar until light and fluffy.

Beat in the eggs, one at a time, followed by the sour cream (or Greek yogurt), lemon zest, and lemon juice. Mix until smooth.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined.

Gently fold in the chopped rhubarb.

Pour the batter into the prepared loaf pan and smooth the top.

Bake for 50–60 minutes, or until a toothpick inserted in the center comes out clean.

Allow the loaf to cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.

In a small bowl, whisk together powdered sugar and lemon juice until smooth. Drizzle the glaze over the cooled loaf.

Let the glaze set before slicing and serving.