This Confetti Gooey Butter Cake Is the Mash-Up Dessert of Your Childhood Dreams

Melt the remaining 1 stick unsalted butter in the microwave or on the stovetop. Add the melted butter, buttermilk, and 1/2 cup vegetable oil to the flour mixture. Beat with the whisk attachment on low speed until combined, scraping down the sides of the bowl with a flexible spatula as needed, about 2 minutes total.