Preheat the oven to 350 degrees F. Grease bottoms only of 2 8x4 inch loaf pans.
Weigh your flour or if measuring by volume, use a light hand and spoon the flour into the cup before leveling.
In a large mixing bowl, combine the flour, sugar, poppy seeds, baking powder and salt.
In a second bowl, whisk together the eggs, milk, oil, orange zest and vanilla.
Add the liquid mixture to the flour mixture and stir until smooth. Pour into the loaf pans, dividing evenly among the two, and bake for 1 hour at 350 F.
Let loaves cool. While they are cooling, mix together the ¼ cup orange juice and the powdered sugar. Add a tiny splash of vanilla. Prick the loaves all over the top with a skewer, then slowly pour the glaze over the loaves. Let them cool completely.
Notes
If you halve the recipe, use 1 large egg plus 2 tablespoons of lightly beaten egg or try 1 jumbo egg plus 1 yolk.