Bring butter, eggs, and yogurt to room temperature. Grease and lightly flour an 9 x 5 x 3 inch loaf pan. In a medium bowl stir together flour, baking powder, and baking soda .Set aside. In a large bowl beat butter with an electric mixer on medium to high speed about 30 seconds or until softened. Gradually add sugar, 2 tablespoons at a time, beating on medium to high speed about 6 minutes total, or until very light and fluffy. Add vanilla, lemon peel, and lemon juice. Then add eggs, one at a time, beating on low to medium speed for 1 minute after each addition; scraping sides of bowl often. Alternately add the flour mixture and yogurt beating on low speed just until combined. Fold in poppy seed. Spread batter in the prepared pan. Bake in a 325F oven for 1 to 1 1/4 hours or until cake test done. Cool cake in pan on a wire rack for 10 minutes. Remove cake from pan and cool completely. Sift powdered sugar over the top.