Preheat your oven to 350°F and grease the pans, lining them with parchment paper.
In a (medium) bowl, mix baking powder, flour, salt and baking soda. Set aside.
In a bowl, cream the butter until creamy. Add sugar and beat until fluffy. Mix in the eggs and yolks one at a time, followed by the vanilla.
In a cup, combine lemon juice and milk.
Alternate adding flour and milk to the butter mixture, starting and ending with flour. Mix until just combined, avoiding overmixing.
Share the batter into the pans, avoiding overfilling.
You should bake for 20 minutes or until a toothpick comes out clean. Let cool in the pan for 10 minutes before transferring to a wire rack to cool completely.
For The Frosting:
Melt butter and stir in cocoa powder until combined.
Start and end with powdered sugar, then add milk alternately.
Beat until fluffy, then stir in vanilla.
Add black food colouring and mix until combined to achieve the desired colour.
For The Candy Pants:
Line the bottom of the (6-inch) cake pan with parchment paper. Draw a half-circle shape across the centre of the pan's bottom half.
Flip the parchment paper over, placing the pencil markings on the bottom, and then lay it on the counter.
Place red candy melts in a piping bag and microwave them. Squish and move the bag every 30 seconds to ensure even melting.
Pipe the red candy melts onto the parchment paper following the drawn lines. If necessary, spread them out with a spatula.
Let the candy melt for 15-20 minutes.
Melt yellow candy melts in a piping bag in the microwave. Squish and move the bag every 30 seconds for even melting.
For the buttons, pipe two oval shapes onto the red candy half circle. For 5-10 minutes, let them sit.