Turn the oven to 350°F (180°C).
Butter and flour (or use baking spray) a 9-inch (24cm) round cake pan with a removable bottom, and put it in the fridge while making the batter.
In a large bowl beat ¾ cup unsalted butter for 20-30 seconds, until creamy.
Always beating, add 1 ¼ cups sugar gradually and beat for 3-4 more minutes, until light and creamy. This is important for a fluffy cake.
Add 3 eggs, one at a time, beating well each time. Add 2 teaspoons vanilla extract and mix everything well.
Sift the dry ingredients (2 cups all-purpose flour, 2 teaspoons baking powder, and ¼ teaspoon salt) and add them to the previous mixture in 3 parts, alternating with ¾ cup whole milk in 2 parts. This means you start and end with flour.
Mix everything very well (I use a spatula) and if you use the electric beaters do so at low speed; you do not want to beat much at this point as that will toughen the cake after it’s baked.
Pour the mixture into the prepared cold pan (which was in the fridge) and bake for about 40 minutes, or until a tester comes out dry.
Let cool on a metal rack until lukewarm enough to remove.
Let cool completely.
It keeps for a few days in the fridge and can be frozen for 1 month, well wrapped in both cases.
If you want to fill it I recommend doing it the next day. Also, a cold cake that has been in the refrigerator is easier to fill and frost.