1. Preheat oven to 350°F (175°C) and grease or line an 8.5 x 4.5-inch loaf pan.

2. In a medium bowl, whisk together flour, baking powder, and salt; set aside.

3. In a large bowl, cream softened butter and granulated sugar until pale and fluffy.

4. Beat in eggs one at a time, then mix in vanilla extract, lemon zest, and lemon juice.

5. Fold in plain yogurt or sour cream and sourdough discard until combined.

6. Add dry ingredients in two additions, mixing gently until no streaks of flour remain.

7. Pour batter into prepared pan, smooth the top, and tap to release air bubbles.

8. Bake for 45-50 minutes or until a toothpick inserted in the center comes out clean.

9. Let the loaf rest in the pan for 10 minutes, then transfer to a cooling rack and cool for 20-30 minutes.

10. In a small bowl, whisk powdered sugar with 1-2 tablespoons lemon juice until pourable.

11. Drizzle glaze over the warm loaf and garnish with additional lemon zest if desired.