In a medium saucepan set over low-medium heat, simmer the champagne until it has reduced to half its volume. Do not let it boil. Leave to cool to room temperature.
1 cup pink champagne
Preheat the oven to 325°F (160°C). Line a 12-count cupcake tin with paper liners. Set aside.
In a medium bowl, whisk the flour, baking powder, and salt together. Set aside.
1½ cups all-purpose flour, 1½ teaspoons baking powder, ¼ teaspoon kosher salt
In a large bowl, using a handheld mixer, beat the sugar, oil, and butter on medium-high speed until smooth and creamy, about 2 minutes. Scrape down the sides and bottom of the bowl as needed.
1 cup granulated sugar, ¼ cup vegetable oil, ¼ cup unsalted butter
Add the eggs and vanilla. Whisk on medium-high speed until combined, about 30 seconds. Scrape down the sides and bottom of the bowl as needed.
2 large eggs, 1 teaspoon pure vanilla extract
With the mixer on low speed, add the dry ingredients in 2 batches, adding the buttermilk in between batches and mixing just until combined after each batch.
2 tablespoons buttermilk
With the mixer still running on low, slowly add the reduced champagne and whisk until combined. Do not overmix. Scrape down the sides and up the bottom of the bowl as needed.
¼ cup reduced pink champagne
Pour the batter into the cupcake liners – fill only ⅔ full to avoid spilling.
Bake for 20-22 minutes, or until a toothpick inserted in the center comes out clean. Allow the cupcakes to cool completely.