Set the oven to 350°F (175°C). Grease a 9-inch cake pan with butter and lightly dust it with flour, or line it with parchment paper.
Beat softened butter and sugar together until the mixture turns light and fluffy. Add eggs one at a time, mixing well after each addition. Stir in the vanilla extract.
Whisk flour, baking powder, and salt together. Add this dry mixture to the butter mixture, alternating with milk, starting and finishing with the flour. Stir gently until smooth and free of lumps.
Pour the batter into the prepared pan and level the surface. Bake for 35–40 minutes, or until a toothpick inserted in the center comes out clean.
Let the cake rest in the pan for 10 minutes, then transfer to a wire rack to cool completely. Serve plain or with fruit, tea, or coffee.