Preheat oven to 350F.
Prep your Bundt pan or tube pan (I like to use baking spray).
Whisk together flour, baking powder, orange zest, and salt in a bowl.
Beat together butter and granulated sugar in another bowl with an electric mixer at medium speed until pale and fluffy, 2 to 3 minutes.
Beat in eggs until combined. Reduce speed to low, then add flour mixture and
eggs until combined. Reduce speed to low, then add flour mixture and poppy seeds and mix until just combined.
Transfer batter to cake pan, smoothing top, and bake until a wooden pick inserted in center of cake comes out clean and top is golden brown, about 30 minutes.
Cool cake in pan on a rack 5 minutes, then invert onto rack.
Whisk together confectioners sugar and orange juice in a bowl until smooth (add more confectioner's sugar or juice a teaspoon at a time if it's too thick or too thin until you get desired consistency).
Pour glaze over warm cake, spreading it with a spatula to drizzle over edge. Let stand until glaze is set, about 15 minutes.
Serve warm or at room temperature.