In a medium bowl, combine the flour, baking powder, and baking soda; set aside. In a stand mixer with the paddle attachment, cream the butter, sugars, and salt together on medium speed until creamy, about 3 minutes.
At low speed, beat in the peanut butter until combined. Scrape down the sides and up the bottom of the bowl with a rubber spatula. Add the egg and pure vanilla extract. Turn the mixer up to high and beat until combined, about 1-2 minutes. Scrape down the sides and up the bottom of the bowl with a rubber spatula again.
At low speed, add the dry ingredients. Mix until just combined, do not over-mix! Cover tightly and chill the cookie dough until firm enough to roll, about 1 hour or up to 3 days.
How to Assemble Peanut Butter Blossoms
Line (2) baking sheets with parchment paper; set it aside. Place ½ cup of granulated sugar in a small bowl. Roll the cookie dough into 1-inch balls (about 1 tablespoon each), roll them in sugar, and place 2 inches apart on the prepared baking sheet; chill them for a least 15 minutes.
Preheat the oven to 350 °F. Bake one batch of cookies until the edges of the cookies are set and lightly golden, about 8 to 9 minutes; while the first batch bakes, keep the remaining batch chilled.
Remove the sheet from the oven and lightly press a candy kiss into the center of each cookie, allowing it to crack slightly. Return to oven until light golden brown, 2 minutes; do not overbake! Remove from the oven, let it cool on the baking sheet for a few minutes, then transfer to a cooling rack to cool completely.