Preheat oven to 350°F. Grease a 9-inch round cake pan. Optionally, line the bottom with a round of parchment paper for easy removal.
In a large bowl, beat butter and granulated sugar together with a hand mixer or stand mixer on medium speed for 1 to 2 minutes, until creamed, pale, and fluffy. Add eggs and vanilla extract, and mix until smooth and creamy.
In a separate bowl, whisk together the flour, baking powder, and salt until combined.
Add half the dry ingredient mixture to the butter mixture and mix gently until just incorporated. Add half the milk and mix gently. Repeat with remaining dry ingredients and milk. Do not overmix - stop as soon as the batter comes together.
Pour batter into the prepared cake pan and smooth the top. Bake for 26 to 32 minutes, or until a toothpick inserted in the center comes out with crumbs (not wet batter), or the top springs back when gently pressed.
Cool cake in the pan on a wire rack. Once fully cooled, turn out onto a serving plate. Dust with confectioner's sugar just before serving.