In a stand mixer fitted with a paddle attachment. Add in the eggs and sugar. Beat on medium until pale yellow. About 2 minutes. Next add in the vanilla, oil, butter, buttermilk, sour cream, zest & juice. Be sure to scrape the sides of the bowl down after each addition. Beat just until combined. Lastly, fold in the poppy seeds. Pour the batter into a lightly greased loaf pan lined with parchment paper. Bake for 40-45 minutes, until the center is set. Allow the loaf cake to completely cool before glazing. Once the glaze sets, slice & enjoy!