I have had a love affair with BettyCrocker.com for years! This is one of my favorite birthday cakes to make myself (I am a little OCD). Anyway, the more lemon the better in my mind. I usually frost it with a traditional butter cream or a lemon scented frosting, it's yummy!
Heat oven to 350°F (325°F for dark or nonstick pan). Make cake as directed on box for 13x9-inch pan. Cool 15 minutes.
Mix lemonade concentrate and powdered sugar. Pierce top of warm cake every 1/2 inch with long-tined fork, wiping fork occasionally to reduce sticking. Drizzle lemonade mixture evenly over top of cake. Run knife around sides of pan to loosen cake. Cover and refrigerate about 2 hours or until chilled.
Spread frosting over top of cake. Sprinkle with sugar. Store covered in refrigerator.