Preheat oven to 350 ℉. Grease and line a 9x5 loaf pan with parchment paper. In a large bowl, add sugar and lemon zest. Rub together with your fingers until sugar is moist and fragrant. Add butter, buttermilk, yogurt, extract and eggs. Whisk until smooth.
Add flour, baking powder, baking soda, salt and poppyseeds. Whisk just until combined. Pour batter into prepared pan. Bake for about 40 minutes or until a toothpick inserted into the center comes out clean. If the bread is browning quickly, but underdone place foil on top to help prevent browning.
Let the bread cool in the pan for 5 minutes before removing to a cooling rack to cool completely. To make the frosting, stir together all ingredients. Pour over the cooled bread and spread out evenly with the back of a spoon. Slice and enjoy!