Set two racks in the upper middle and lower middle positions and preheat the oven to 350 degrees. Use parchment paper to line two baking sheets.

In a stand mixer, beat the butter and sugar for about five minutes at medium speed, or until light and fluffy. Add the vanilla and egg after scraping the bowl's sides.

In a sizable basin, mix the flour, salt, and baking pan. Low-speed down the mixer's speed. Half a cup at a time, add the dry ingredients to the butter mixture, alternating with the milk, starting and finishing with the flour.

Pour the batter onto baking sheets that are 2 inches apart in all directions using a 1/4 cup measuring cup. There ought to be 12 cakes currently. (Make them with 2 tbsp each if you want smaller cakes. You'll use one additional baking sheet.)

Bake for 15 to 18 minutes at 350 degrees, turning the baking pans halfway through. (For smaller cakes, reduce cooking time to 10–13 minutes.) A cake tester should come out clean when the cakes are thoroughly baked, although they will still be mushy. Take out and place on a cooling rack to cool entirely.