Preheat oven to 350F. Lightly grease and flour a nonstick 9-in bundt cake pan. Set aside.
Place butter and sugar in a large bowl. Beat on high speed with a handheld mixer until smooth. Beat in lemon juice, zest, yogurt, eggs, buttermilk, and vanilla until smooth.
In a separate bowl, combine flour, baking soda, baking powder, salt, and poppyseeds. Gently fold flour mixture into liquid until batter is just combined.
Scrape batter into prepared pan and smooth top. Bake cake at 350F 45-50 minutes or until a skewer inserted in middle comes out clean. Cool cake in pan completely, then invert onto a serving plate.
Make the glaze: Whisk glaze ingredients in a small bowl until a thick glaze forms. Drizzle glaze over cooled cake and let stand 10 minutes before cutting and serving. Enjoy!