01 -
In a medium bowl, stir flour, baking powder, baking soda, and salt together until well mixed.
02 -
Use your stand mixer with paddle attachment or grab a hand mixer to beat the butter and sugar until fluffy.
03 -
Blend in the sourdough starter, egg yolk, lemon juice, lemon zest, vanilla, and food coloring if you're using it until everything's smooth.
04 -
Add the flour mix bit by bit until everything's mixed well.
05 -
Wrap the bowl with plastic and stick it in the fridge for at least 2 hours but you can leave it there up to 3 days.
06 -
Heat your oven to 350°F and put parchment paper on your baking sheet. Shape the dough into 1-inch balls and roll them generously in powdered sugar.
07 -
Put them in the oven for 11-13 minutes until the edges look done and middles are puffy but still soft. Let them cool about 5 minutes before you eat them.