Oven to 350 deg F

Loaf tin butter and flour. Whisk flour, baking powder and salt in medium bowl. Using your fingers, rub sugar with lemon zest until sugar is moist. Add yogurt thinned a little with water, veg oil, eggs, and vanilla extract. Whisk to blend.
Fold in dry ingredients until just combined. Pour batter into pan.

Bake 45 to 50 minutes