Preheat the oven to 350 degrees. Line an 8x8 pan with parchment paper so that there is an overhang on two sides.
Place the vegan buttery spread and sugar in a mixing bowl and mix on medium speed until fluffy.
Add the unsweetened applesauce and vanilla extract and mix until combined.
Stop the mixer and add the gluten free flour blend, powdered sugar, baking powder, and salt.
If the dough looks too dry, add a little more applesauce or a splash of water. The batter should be thick and lumpy, but not dry.
Place the dough in the parchment lined pan and use a piece of waxed paper to smooth and press the batter evenly into the pan.
Bake at 350 degrees for 25-28 minutes.
Make the frosting:
If you'd like to use dried fruit to color the frosting, place the dried berries in a mini food processor and blend on high until they become a fine powder.
Sift them with a fine mesh sieve, discarding any larger crumbs. Set the powder aside.
Once the cookie bars are cool, make the frosting. Beat the vegan buttery spread until fluffy, then sift in about a ½ cup of sifted powdered sugar. Mix until combined, then alternate adding more sifted powdered sugar and a little water. Add the powdered berries if you are using them. I used about 1 ½ Tablespoons of dried blueberry powder to achieve the color in the photos.
The frosting should be thick and spreadable. Frost the cooled bars, then cut into 12 pieces.
Notes
Allow the bars to cool fully before frosting and slicing.You don't have to frost these - you could drizzle melted chocolate on top, or dust with powdered sugar, or place sliced strawberries on top. This is a very versatile recipe.Store cookie bars in an airtight container. They should stay fresh for 3-4 days.