Preheat the oven to 375°F and lightly spray a mini muffin tin with baking spray.
Mix together the flour, baking soda, and baking powder in a small bowl. Set aside.
In a large bowl, beat the soft butter and 1 ¼ cups sugar until fluffy and light. Add egg and vanilla extract, mixing until fully incorporated.
Gradually mix in the dry ingredients until just combined.
Roll the dough into 1-inch balls and place in the muffin cups. Bake for 8-10 minutes or until golden brown. Press down with a spoon to create a well and cool.
For the lemon curd, beat together 6 tablespoons butter, 1 cup sugar, and 2 eggs. Stir in lemon juice and cook over medium heat for 5 minutes until thick.
Let the lemon curd cool for a few minutes, then spoon a teaspoon into each cookie cup.
Top with lemon zest and refrigerate for 30 minutes to set the curd. Dust with powdered sugar before serving.