January 27, 2016 4 Comments


Birthday Cake Protein Blondies… because today is someone‘s birthday somewhere. I have made blondies like this before, but this recipe takes the cake (pun intended)! The texture is more dense than “cakey,” with a soft crumb and thick, creamy frosting. The flavor tastes just like real birthday cake with sugar, vanilla, and sprinkles. SO GOOD. They didn’t last more than a day at our house! Hard to believe they’re low in fat and carbs, gluten-free, and high in protein.

You might also like my Carrot Cake Protein Slices!


Which type of whey is best for baking?

The protein powder I used in this recipe is Quest Protein Powder in Vanilla Milkshake. You can really use any brand of protein powder so long as it’s a whey concentrate or whey blend. I don’t recommend baking with whey isolate because it really dries out baked goods and gives them a crumbly texture. Collagen and vegan protein powders behave so differently compared to whey, there is no substitution I can give.


Sweetener substitutions

For that birthday cake sweetness, I added my favorite organic, calorie-free stevia blend that’s twice as sweet as sugar. Feel free to use any sweetener you like! Keep in mind, if you use erythritol, monk fruit, baking stevia or another sweetener that measures 1-to-1 like sugar, you’ll need twice as much (two-thirds cup).

Flour substitutions

I used coconut flour to keep the carbs low, but you can substitute twice as much (one-quarter cup) gluten-free baking flour, gluten-free oat flour, or cassava flour (Paleo). You could also try a quarter cup of all-purpose flour, cake flour, or sweet white sorghum flour. If substituting almond flour, you will likely need 3-4 times as much, so start with six tablespoons but you may need up to half a cup.


Other ingredients

Nonfat plain Greek yogurt replaces the butter or oil you’d normally find in a blondie recipe, adding moisture and protein without the excess fat! Because this recipe relies a lot on the yogurt, I don’t recommend substituting it for anything else (even cottage cheese). You can use a flavored Greek yogurt, like Vanilla Chobani Simply 100, if you like.

I also added some cashew butter, but you could also use white chocolate peanut butter which tastes phenomenal!

Frosting substitutions

Last but not least, the frosting. For the frosting I simply combined Greek cream cheese (found this at Walmart), confectioner’s erythritol (a sugar-free alternative to powdered sugar), a little Quest Protein Powder in Vanilla Milkshake, and vanilla extract. The frosting is amazing! If you can’t find the Greek cream cheese, neufchâtel cheese or reduced fat cream cheese would also work. You can even use dairy-free cream cheese!

Instead of the confectioner’s erythritol, you can also use powdered monk fruit blend, powdered sugar, granulated erythritol, monk fruit, baking stevia, or half as much of my favorite stevia blend.

Now, here’s the recipe for these Birthday Cake Protein Blondies! Please comment below if you try these – I always love your feedback 🙂

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Birthday Cake Protein Blondies

These Birthday Cake Protein Blondies taste like confetti birthday cake while being low in fat and carbs, gluten-free, and high in protein.
Course Dessert
Prep Time 10 minutes
Cook Time 20 minutes
Servings 8 servings
Calories 128kcal


  • 1/3 cup (40g) whey blend protein powder* I used Quest Protein in Vanilla Milkshake
  • 1/3 cup calorie-free sweetener* I used one twice as sweet as sugar
  • 2 tbsp. coconut flour*
  • 1/4 tsp. baking soda
  • Dash salt optional
  • 1/2 cup nonfat plain Greek yogurt
  • 2 tbsp. cashew butter*
  • 2 tbsp. (1 large) egg white
  • 1 tsp. melted coconut oil optional
  • 1/2 tsp. pure vanilla extract
  • 2 tsp. sprinkles optional


  • 3/4 cup (6 oz.) Greek cream cheese* or whipped or reduced fat cream cheese
  • 25 g whey blend protein powder* I used Quest Protein in Vanilla Milkshake
  • 1/2 cup powdered calorie-free sweetener*
  • 1/4 tsp. pure vanilla extract

Additional topping

  • 1 tsp. sprinkles optional


  • Preheat oven to 350 degrees F.
  • Whisk together dry ingredients (through salt) in a medium mixing bowl.
  • Mix in wet ingredients (through vanilla). Batter will be thick!
  • Gently stir in sprinkles. Don’t stir too much or the colors will bleed into the batter.
  • Scoop batter into a 7"x5" baking dish lightly coated with cooking spray or lined with parchment (recommended).
  • Bake for 15-20 minutes until center is set but a toothpick or knife inserted comes out a little gooey.
  • While blondies cool, combine frosting ingredients. Frosting will seem too thick at first, but keep working it until creamy.
  • Spread over blondies and add sprinkles if desired. Store in the fridge until ready to eat.


Calories (including optional ingredients): 128kcal, Fat: 5.9g, Sat fat: 2.6g, Carbs: 7g, Fiber: 1g, Sugar: 4g, Protein: 12g, Sodium: 159mg
Calories (minus optional ingredients): 116kcal, Fat: 5.5g, Sat fat: 2.1g, Carbs: 6g, Fiber: 1g, Sugar: 3g, Protein: 12g, Sodium: 123mg

4 Responses

Sarah Wilkins
Sarah Wilkins

October 21, 2022

Hi Kelly! I used a 7″×5″ glass Pyrex baking dish – and yes, if using unflavored protein you would want to add up to half a cup of sweetener and one teaspoon of vanilla extract.


October 21, 2022

I’m so excited to make this. Can you clarify what size the baking dish needs to be? Also, I have the Quest non-flavored/multi-purpose whey powder. I’m assuming I just add more sweetener and vanilla extract to the batter? Thanks!

Sarah Wilkins
Sarah Wilkins

April 04, 2022

I am sorry about that! When I switched platforms the original “print” buttons stopped working. I’ve been going through updating them one by one! You can also just copy the recipe and paste to a blank page then print. Hope that helps!


April 04, 2022

Hello! I’m very excited to try this Birthday Cake Protein Blondie recipe, but when I click on the PRINT icon it says “page not found.”

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