Preheat your oven to 350°F (175°C).
In a bowl, sift together the flour and baking powder, then whisk to combine.
In a stand mixer fitted with a paddle attachment, cream the butter and sugars until light and fluffy.
Optional: Add ¼–½ teaspoon of sea salt for a hint of extra flavor.
Mix in the peanut butter until fully incorporated.
Beat in the egg and vanilla extract until the mixture is smooth and well combined.
Gradually add the flour mixture, mixing just until everything is incorporated.
Roll the dough into 1-inch balls and place them on a baking sheet lined with parchment paper.
Use a fork to gently flatten each ball, creating a criss-cross pattern on top.
Bake for about 10 minutes, or until the edges turn a light golden color.
Let the cookies cool completely on the baking sheet to set properly.