In the bowl of a stand mixer fitted with a paddle attachment, beat the eggs and sugar together. Add milk, oil and vanilla. In a large bowl, combine the flour, baking powder and salt. Slowly add the dry ingredients to the wet ingredients in the mixer, one cup at a time, mixing well after each addition.
Form the dough into a disc, wrap in plastic wrap and refrigerate for at least 1 hour.
Preheat oven to 350 degrees. Line two baking sheets with parchment paper.
Using a rolling pin, roll dough out on a lightly floured surface until 1/8-inch thickness. Cut out circles using a 3-inch biscuit cutter or martini glass. Dip your fingers in water and dampen the edges of each circle. Place 1-2 cherries in the center of each circle. Pinch the edges of the dough together in 3 points to make the shape of a triangle. Be sure that the edges are sealed.
Transfer the unbaked cookies to the prepared baking sheets.
Whisk the egg yolk in a small bowl. Brush the dough with egg wash. Bake for 16-18 minutes or until golden brown. Transfer to a wire rack from the cookie sheet. Allow to cool on the wire rack.