Preheat your oven to 350°F/180°C. Prepare your 12 cup muffin pan by lining it with 12 cupcake liners. This is essential to ensure your cupcakes don’t stick.
In a large bowl, using an electric hand mixer, cream together the ½ cup unsalted butter and ¾ cup granulated sugar at medium speed until the mixture is lighter in color and smooth. This should take about 3 to 5 minutes. The goal here is to incorporate air into the butter for fluffiness.
Add the 2 large eggs, one at a time, mixing well after each addition. It’s important that they’re at room temperature to blend well with the butter. Then, stir in 1 ½ teaspoons pure vanilla extract and ½ cup yogurt, mixing until everything is well incorporated.
In a separate medium bowl, whisk together 1 ¼ cups all-purpose flour, 1 teaspoon baking powder, and ¼ teaspoon salt. This dry mix is critical to ensure even distribution of the leavening agents.
Gradually pour about one-third of the dry ingredients into the wet ingredients, mixing with the electric mixer until just combined. Then add the remaining dry ingredients along with ¼ cup sprinkles. Be careful not to overmix; you want a light batter.
Using a spoon or a cookie scoop, fill each cupcake liner halfway with the batter. This prevents overflow and ensures they bake evenly.
Place your muffin pan in the preheated oven and bake for about 20 minutes or until a toothpick inserted into the center of one of the cupcakes comes out clean. Keep an eye on them toward the end to avoid overbaking!
Once baked, allow the cupcakes to rest in the pan for about 5 minutes before transferring them to a wire rack to cool completely.
While the cupcakes are cooling, prepare the buttercream frosting. In a large bowl, cream together another ½ cup unsalted butter until smooth. Gradually add 2 cups powdered sugar, mixing until fluffy.
Add 2 tablespoons heavy cream, 1 teaspoon pure vanilla extract, and ½ teaspoon salt. Mix until creamy. If needed, adjust the consistency with more cream or sugar.
Once the frosting is ready, take about ¼ cup of the buttercream and set it aside. Add blue food coloring to the remaining frosting, mixing until you achieve your desired shade of blue.
To decorate, start in the center of each cupcake and pipe a continuous spiral of frosting until the cupcake is covered. Then, use the white frosting you set aside to pipe clouds around the base of the rainbow.