Preheat oven to 350°F. Line a muffin pan with paper or parchment liners. Set aside.
In a medium bowl, whisk together cake flour, baking powder, baking soda and salt. Set aside.
1¼ cups cake flour, ¾ teaspoons baking powder, ½ teaspoon baking soda, ½ teaspoon salt
Add eggs to a large bowl or the bowl of a stand mixer and and beat 10-20 seconds. Add granulated sugar and continue to beat on medium speed about 30 seconds.
2 eggs, 1 cup granulated sugar
Add vanilla extract and oil and continue beating until combined.
1½ teaspoons vanilla extract, ½ cup oil
Reduce mixer speed to low and slowly add about half of the flour mixture.
Add the milk, then the rest of the flour and the sour cream. Beat until just combined, scraping down the sides and bottom of the bowl as needed. The batter will be thin.
⅓ cup milk, ⅓ cup sour cream
Gently fold the sprinkles into the batter until even distributed.
⅓ cup rainbow jimmies
Evenly fill the liners until about two-thirds full. Bake cupcakes for 12 to 14 minutes or until an inserted toothpick comes out with a few moist crumbs and the tops of the cupcakes spring back when gently pressed.
Cool cupcakes in the pan for a few minutes, then remove cupcakes from pan (carefully) and finish cooling on a wire rack.
Frost with buttercream frosting or cream cheese frosting and finish with more sprinkles on top. Enjoy! 1 batch buttercream frosting, 3 tablespoons rainbow sprinkles