Preheat the oven to 350°F and place a rack in the center. Line two baking sheets with parchment paper.
Sift the flour, baking powder, and salt together in a large mixing bowl and set aside.
In another mixing bowl, combine the eggs and sugar, then beat until combined. Add milk, melted butter, and lemon zest, and beat until smooth.
Add the dry ingredients slowly to the wet mixture until all is added and the batter is combined.
Add additional flour by the tablespoonful if the batter is too sticky.
Using your hands, roll the dough into smooth balls about the size of apricots or walnuts. Depending on the size of the balls, you will have about 44 to 48.
Place the balls an inch apart on the baking sheets.
Gently press down on the balls to flatten the bottoms, while still leaving a round dome on top.
Bake one sheet at a time for 15 minutes. Turn the pan around after half the cooking time. The cookie bottoms will be light brown, and the tops will remain pale.
After removing from the oven, let the cookies cool slightly. Then take a knife and cut a circle in the bottom of the cookies, being careful not to break or cut through them. Take a small spoon and scoop out some of the cookie inside.
After the cookies have completely cooled, spoon the ricotta mixture into each of them. For half the cookies, place an almond on top of the filling to represent a peach pit. Take two halves, one with almond and one without, and place them together, squeezing some of the filling outside. This will seal the cookies into one. Wipe off any excess filling.