Heat oven to 350°F. Line two baking sheets with parchment.
Whisk flour, baking powder, and salt in a bowl; set aside.
Cream butter and sugar until light and fluffy, about 2 minutes.
Beat in eggs one at a time. Mix in ricotta, vanilla, and lemon zest until smooth.
Fold dry ingredients into the wet mixture just until combined. Do not overmix.
Scoop rounded tablespoons of dough onto sheets, spacing about 2 inches apart.
Bake 11–13 minutes, until set and barely golden at the edges. Cool completely on racks.
Whisk powdered sugar, lemon juice, milk, and vanilla until thick yet pourable.
Dip or spoon glaze over cooled cookies. Add sprinkles before the glaze sets.
Let glazed cookies stand 20–30 minutes until the icing firms.