Best Marshmallow Cake - How To Make A Marshmallow Cake

Ingredients

• Cooking spray
• 2 c. all-purpose flour
• 3/4 c. unsweetened cocoa powder
• 1 tsp. baking soda
• 1 tsp. kosher salt
• 1 c. hot coffee
• 1 c. granulated sugar
• 1/2 c. packed brown sugar
• 3/4 c. vegetable oil
• 1/2 c. sour cream, room temperature
• 3 large egg whites, room temperature
• 1/4 tsp. cream of tartar
• 1 1/2 c. granulated sugar
• 3/4 c. water
• 1 tsp. pure vanilla extract