Position a rack in the center of the oven and pre heat to 350 deg F. Butter a 9x5 loaf tin, line the bottom with parchment paper and butter the parchment.
Finely grate enough zest to yield 2 Tbs and then squeeze the oranges to yield 1 cup strained juice. Set aside 1/4 cup of juice for the glaze.
Ina medium bowl, whisk the flour, baking powder and salt.
In a mixer beat the butter and sugar until light and fluffy, about 2 mins. Add the eggs one at a time, beating on medium speed until incorporated and scraping down the sides of the bowl as necessary. Add the vanilla and orange zest and beat until incorporated (the mixture may look curdled at this point). With the mixer on low, alternatly add the flour mixing in three additions, and the 3/4 cup orange juice in 2 additions, beginning and ending with the flour.
Scape the batter into the prepared pan, smooth the top. Bake until a tester inserted in the center comes out clean, 45 mins to 1 hr.
Let the cake cool in the pan for 10 minutes, run a knife around the sides, invert onto the rack, remove the parchment paper and invert again.
In a small bowl whisk the reserved orange juice with a pinch of salt and the confectioners sugar until smooth. Set the warm cake on it's rack over a baking sheet. Using a toothpick. poke holes at 3/4 inch intervals in the top of the cake, stopping about 3/4 of the way down the cake.
Repeatedly brush the glaze evenly over the top and sides until you have used it all. Cool the cake 2 hours before slicing.
Store at room temperature, wrapped in plastic for up to three days.