Preheat Oven: Preheat your oven to 350°F (175°C). Line a 12-cup muffin tin with cupcake liners.
Mix Dry Ingredients: In a medium bowl, whisk together the flour, baking powder, baking soda, and salt.
Combine Wet Ingredients: In a large bowl, beat the eggs and sugar together until light and fluffy. Add the vanilla extract and vegetable oil, mixing until well combined.
Add Buttermilk and Dry Ingredients: Gradually add the dry ingredients to the wet ingredients, alternating with the buttermilk, beginning and ending with the dry ingredients. Mix until just combined.
Bake Cupcakes: Divide the batter evenly among the cupcake liners, filling each about two-thirds full. Bake for 15-18 minutes, or until a toothpick inserted into the center comes out clean. Let the cupcakes cool in the pan for a few minutes, then transfer to a wire rack to cool completely.
Prepare the Buttercream Frosting: In a large bowl, beat the softened butter until creamy. Gradually add the powdered sugar, heavy cream, vanilla extract, and a pinch of salt. Beat on high speed until the frosting is light and fluffy. If desired, add food coloring and mix until well combined.
Frost the Cupcakes: Once the cupcakes are completely cool, frost them with the prepared buttercream frosting using a piping bag or a spatula. Decorate with sprinkles.
Serve: Enjoy these delightful birthday cupcakes with friends and family!