Vanilla Small Cake (6" cake)

Name: Vanilla Small Cake (6" cake)
Prep time: 20 min
Cook time: 37 min
Total time: 57 min
Cuisine: American
Ingredients: 6 tablespoons unsalted butter, softened; 1/2 cup granulated sugar; 1 large egg; 1 tablespoon vanilla extract; 3/4 cup all-purpose flour; 1/8 teaspoon fine salt; 1/4 teaspoon baking soda; 6 tablespoons whole milk; 1/2 teaspoon apple cider vinegar*; 8 tablespoons (1 stick) unsalted butter, at room temperature; 2 cups powdered sugar; 2 teaspoons vanilla extract; 1 tablespoon heavy cream