Preheat the oven to 325°F or gas mark 3. Grease the loaf pan and set aside.
In a bowl combine the flour, baking powder, and salt together. Whisk to combine thoroughly. Set aside.
In a stand mixer with paddle attachment beat the butter on medium high speed until smooth. Add the sugars and beat until light in color, at least 5 minutes, scraping the bowl often. Add the eggs one at a time waiting 1-2 minutes between each egg. Scrape the sides down often. Once all of the eggs are incorporated add the vanilla.
Reduce the speed the low and add the flour mixture mixing until all of the flour disappears and incorporated. Be careful not to overmix. Place in the oven and bake for 70-75 minutes or until a knife of toothpick inserted in the center comes out clean.
Cool in the pan for 30 minutes before running knife around the sides. Remove and allow to finish cooling on a cooling rack.