Preheat the oven to 350°F (175°C). Line an 8×8-inch baking pan with parchment paper.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
In a large bowl, cream the 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, fresh 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 baking pan and spread evenly.
Bake for 22-25 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, crumble the cake into a large bowl until fine crumbs form.
Melt 4 ounces of white chocolate in a microwave-safe bowl in 30-second intervals, stirring between each, until smooth.
Add about 3 tablespoons of melted white chocolate to the cake crumbs and mix until the mixture holds together when pressed.
Roll the mixture into 24 equal-sized balls and place them on a parchment-lined baking sheet.
Insert a lollipop stick into each cake ball, about halfway through.
Freeze the cake pops for 15 minutes to firm up.
Melt the remaining 4 ounces of white chocolate in the microwave as before until smooth.
Dip each cake pop into the melted white chocolate, allowing the excess to drip off.
Immediately sprinkle the coated cake pops with rainbow sprinkles before the chocolate sets.
Place the cake pops upright in a styrofoam block or a cake pop stand to dry completely, about 30 minutes.
Once set, serve or store as desired.