Preheat the oven to 350°F (175°C). Line an 8-inch square baking pan with parchment paper, leaving an overhang for easy removal.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
In a large bowl, beat the 1/2 cup softened butter and granulated sugar together until light and fluffy, about 3 minutes.
Add the eggs one at a time, beating well after each addition.
Mix in the sour cream, lemon juice, lemon zest, and vanilla extract until combined.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Do not overmix.
Pour the batter into the prepared pan and spread evenly.
Bake for 22 to 25 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cake to cool completely in the pan on a wire rack.
Once cooled, remove the cake from the pan using the parchment overhang and crumble it into a large mixing bowl.
In a small bowl, combine the powdered sugar, 2 tablespoons softened butter, 1 tablespoon lemon juice, and 1 teaspoon lemon zest to make the lemon frosting. Mix until smooth.
Add the frosting to the crumbled cake and mix thoroughly until the mixture holds together when pressed.
Using your hands or a small cookie scoop, form the mixture into 24 even balls and place them on a baking sheet lined with parchment paper.
Insert a lollipop stick halfway into each cake ball. Chill the cake pops in the refrigerator for at least 30 minutes to firm up.
Melt the white chocolate in a microwave-safe bowl in 30-second intervals, stirring between each, until smooth.
Dip each chilled cake pop into the melted white chocolate, allowing excess to drip off.
Immediately sprinkle the yellow sanding sugar or yellow sprinkles over the wet chocolate coating.
Place the dipped cake pops upright in a styrofoam block or cake pop stand to set.
Refrigerate the cake pops for 15 minutes or until the coating is firm.
Serve and enjoy your bright and zesty lemon cake pops!