It depends! Cake always tastes best at room temperature, so if you're planning on serving and eating your cake within 1-2 days, it's fine to keep at room temperature. So long as you don't live in an extremely hot country anyway! But if you want to keep your cake for longer than 2 days, it's best to keep it in the fridge. Regardless of being kept at room temp or in the fridge however, it should always be kept air-tight.