Gluten Free Black Velvet Cake Recipe (No Food Dyes)

Name: Gluten Free Black Velvet Cake Recipe (No Food Dyes)
Prep time: 45 min
Cook time: 32 min
Total time: 1 h 17 min
Cuisine: American
Ingredients: 1¾ cups (245g) Kim's gluten free all purpose flour blend ((a store bought blend may work, but has not been tested)); 1⅔ cups (340g) granulated sugar; ⅔ cup (80g) black cocoa powder; 2 tsp baking soda; 1 tsp baking powder; ½ tsp kosher salt; ½ cup (120g) vegetable oil ((or any neutral oil)); 2 large eggs, at room temperature; 1½ tsp pure vanilla extract; 1 cup (240g) whole fat buttermilk, at room temperature; 1 cup plus 2 tbsp (270g) very hot coffee or water ((coffee really brings out the chocolate flavor)); 1½ cups (340g) butter, at room temperature ((a dairy-free butter or shortening may be substituted)); 2¾ cups (340g) powdered sugar; ½ cup (56g) black cocoa powder; ¼ cup (60g) hot coffee; 2 tsp pure vanilla extract; ¼ tsp salt, or to taste; 5 oz (142) marshmallow cream or fluff; ¾ cup (94g) powdered sugar; 6 tbsp (85g) butter, softened ((a dairy-free butter may be substituted)); ½ tsp vanilla extract; ¼ tsp kosher salt; 25-30 mini marshmallows ((or 2-3 large ones))