Preheat your oven to 350°F (175°C). Grease and flour a cake pan.
In a mixing bowl, whisk together flour, sugar, poppy seeds, baking powder, and salt.
In another bowl, beat the butter until creamy. Add eggs one at a time, beating well after each addition.
Mix in milk, vanilla extract, orange zest, and juice.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Pour the batter into the prepared cake pan. Bake for 40 minutes or until a toothpick inserted into the center comes out clean.
Let the cake cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.