Preheat the oven to 180C/350F. Grease an 8 x 8-inch dish and set aside.
In a small bowl, whisk together the dry ingredients and set aside. In a separate bowl, cream together the butter and brown sugar, then add in the applesauce and vanilla extract. Gently fold through the dry ingredients into the wet, then add the rainbow sprinkles.
Transfer to the baking dish and bake the blondies for 20-25 minutes, or until mostly set in the middle or a skewer comes out clean.
Remove them from the oven and let them cool completely, before frosting and slicing.
Notes
* Or 2 cups of rolled oats ground to a flour-like consistency.** Or a sugar substitute, like keto brown sugar.*** Betty Crocker frosting is naturally gluten free and vegan. Any frosting works. TO STORE: Store leftovers in the refrigerator, covered, for up to one week.TO FREEZE: Place blondies in an airtight container and store them in the freezer for up to 6 months.