Preheat oven to 375 degrees F.
In a stand mixer cream the butter or plant based butter stick with sugar and vanilla. Mix for a full minute or until good and fluffy.
Beat in eggs, one at a time, and fully mix after each egg.
Mix in salt and baking powder dissolved in 1 tablespoon warm water.
Finally, add in the flour. Stir in flour until just combined, scraping the bowl periodically. The dough should be smooth and thick but also pliable. If it feels too stiff add another tablespoon of warm water.
Working with about half to ⅓ of the dough at a time, roll the dough pretty thin; about ¼" inch. You may need to lightly flour your surface.
Cut out into circles using a cookie cutter or drinking glass.
Fill each circle with no more than a heaping teaspoon of filling and fold into triangles. Pinch corners well so they will keep their shape.
Place cookies on lined baking sheet about 2 inches apart. Bake 9-12 minutes until just starting to turn golden.
Allow to cool for at least 10 minutes.