1. Preheat your oven to 350°F (175°C) and line a muffin tin with paper liners.
2. In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
3. In a large bowl, mix the sugar and melted butter until well combined. Stir in the eggs, one at a time, then add the vanilla extract.
4. Fold in the grated cucumber and yogurt, mixing gently until just combined. Be careful not to overmix; the batter should be lumpy.
5. Gently fold the dry ingredients into the wet mixture, stirring until just incorporated. If using lemon zest, fold it in at this stage.
6. Spoon the batter evenly into the prepared muffin tin, filling each cup about three-quarters full.
7. Bake for 18-20 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
8. Allow the muffins to cool in the tin for 5 minutes before transferring them to a wire rack to cool completely.

Baking these muffins with Ouma was always a lesson in patience and precision. She taught me that taking the time to savor each step is what makes the end result so rewarding.