Preheat oven to 350 degrees Fahrenheit
Line a muffin pan with cupcake liners.
Set aside, In a bowl or a measuring cup, combine milk and lemon juice. Mix and set aside.
In a medium-size mixing bowl, combine flour, salt, and baking powder. Mix until combined and set aside.
In a large bowl with a hand mixer, beat the butter and sugar. Mix until it is nice and creamy.
Mix in the egg, and vanilla extract.
Add the milk/lemon mixture and 1/2 of the dry mixture to the wet mixture. Mix until you have no more dry flour.
Finally, add in the cooled coffee and the rest of the dry mixture.
Mix until all dry ingredients are incorporated. Be careful not to overmix.
Fill each of the cupcake liners to ¾ full.
Bake the cupcakes, in the preheated oven for 19-21 minutes. The cupcake should be cooked once a toothpick comes out clean when inserted in the center of the cupcake.
Allow the cupcakes to cool off completely before frosting.