One-Bowl Vanilla Buttermilk Cake

Name: One-Bowl Vanilla Buttermilk Cake
Prep time: 10 min
Cook time: 30 min
Total time: 40 min
Cuisine: Southern, American
Ingredients: 1 ½ cups all-purpose flour; 1 cup granulated sugar; 1 teaspoon baking soda; ½ teaspoon baking powder; ¼ teaspoon salt; 1 large egg; ½ cup vegetable oil; ½ cup whole buttermilk, well shaken; ½ cup hot water; 1 tablespoon vanilla extract; ¾ cup (1 ½ sticks) salted butter, softened at room temperature; 1 ½ tablespoons whole buttermilk or heavy cream; 2 teaspoons vanilla extract; 1 ½ cups powdered sugar; Optional garnish: sprinkles