Preheat the oven to 350º (180°C).
Butter or spray a 9x5-inch loaf pan.
Line with a piece of parchment paper if you want, covering the pan's bottom and two long sides. The two short sides will remain unlined but greased. This will help you remove the cake from the pan.
In a large bowl with an electric mixer (or the bowl of a stand mixer with the paddle attachment), beat butter until pale and fluffy. Gradually add sugar at medium-high speed.
Mix eggs, yolk, milk, salt, and vanilla in a medium bowl. Add gradually to the butter mixture, mixing well.
Add the sifted dry ingredients in three additions, mixing carefully with a spatula. Like me, you might sift flour and baking powder in another bowl or do it directly over the batter.
Integrate well until no lumps remain, but don't overbeat after adding the flour.
Pour into the prepared pan and spread with a spatula to even it out.
Sprinkle with the remaining 1 tablespoon of sugar and bake for 50 to 60 minutes, until a cake tester or toothpick inserted in the center comes out clean.
Let cool on a wire rack, remove from the pan, dust with powdered sugar, and serve.
For storing leftovers see Notes below.