Make the dough: In a large bowl, whisk the flour, baking powder, and salt and set aside. In a stand mixer fitted with a paddle attachment, cream the butter and sugar on medium-low speed until light and fluffy, about 5 minutes. Add eggs and vanilla to the stand mixer and mix until everything is combined. Add the flour mixture and mix, on medium-low, until a moist, extra soft dough is formed. Scoop out the dough and wrap tightly in plastic wrap, refrigerate for at least 2 hours or up to two days.

Prepare the filling: Fill a medium-sized pot with a few inches of water. Turn the heat to medium-low to lightly simmer the water. Place a glass bowl atop the pot (big enough not to fall in) and add all of the lemon curd ingredients. Whisk lightly to incorporate all of the ingredients and then cook for approximately 30 minutes, stirring occasionally. Once the curd has thickened and homogenized, remove the glass bowl and place it into an ice bath to cool. 

Fill and shape your cookies: Heavily flour a clean work surface and roll out the dough until it’s about ¼-inch thick. Feel free to sprinkle more flour if needed to prevent sticking. Use the top of a glass or circle cookie cutter to cut out circles that are about 3 inches in diameter. Drop 1 ½ teaspoons of lemon curd into the center of each circle of dough. Working one by one, dip your finger into a cup of water and lightly wet the circumference of the circle. Fold up two sides to make one point of the triangle. Fold up the remaining flat piece and pinch all three corners tightly so the hamantashen do not open while baking. Place the cookies onto a large parchment lined baking sheet. They can be close together but not touching.

Set the oven to 350 degrees. Place the sheet pan into the freezer for about 15 minutes, then transfer directly into the oven. Bake for about 12-15 minutes until the bottom of the hamantashen are golden brown.