These easy Snickerdoodle Bars have all the cinnamon-sugar flavor of the classic cookie. Topped with a cinnamon frosting, these cookie bars are a crowd-pleaser! Gluten-free, dairy-free, and vegan.
Preheat oven to 350 degrees Fahrenheit. Spray an 8x8 baking pan with cooking spray and line with parchment paper.
In a large mixing bowl, add tapioca starch and water. Whisk to combine. Add melted butter, agave, cane sugar, and vanilla extract. Whisk again to incorporate.
Add almond flour, coconut flour, salt, baking soda, cream of tartar, and cinnamon. Stir with a rubber spatula until you have a cohesive dough. Allow the dough to rest for 2-3 minutes, then transfer it to the prepared pan.
Use the rubber spatula to evenly distribute dough in the pan. Then use an extra piece of parchment paper to lightly press and smooth the dough into an even layer. Make sure all corners are filled.
In a small bowl, combine cinnamon-sugar mixture and sprinkle it evenly over the top of the dough. Use that extra piece of parchment to lightly press the sugar coating into the dough.
Bake for 14-15 minutes. A tester or toothpick should come out clean. The edges will be a golden brown and the top will have started to turn golden. Remove from oven and allow to cool on wire rack.
Once completely cool, refrigerate the bars for at least one hour before frosting. Allow bars to come to room temperature prior to frosting so that the frosting doesn't harden quickly and become difficult to spread.
When ready to frost the cookie bars, add frosting ingredients to a medium mixing bowl. Beat with an electric hand mixer until the frosting becomes smooth.
Gently lift the bars out of pan using parchment flaps and place on a cutting board. Using an offset spatula, frost bars and sprinkle with cinnamon (see notes). Slice into large bars or smaller bite-sized bars.
Notes
After the bars have cooled, wrap the baking pan in foil or plastic wrap to chill. This is the best way to keep the bars from crumbling once sliced. Allow them to come to room temperature before frosting.
Use softened butter for the vegan buttercream frosting for a smooth and creamy consistency.
Dollop all the frosting onto the center of the baked snickerdoodle and spread outward keeping a thick layer between the spatula and top of bar. This will help prevent the top from tearing.
For clean, easy-to-cut slices, remove the uncut bars from the pan using the parchment flaps. Transfer to a cutting board and use a sharp knife to slice small or large squares.
Variation: Omit the frosting. These cookie bars are great with just the cinnamon sugar topping alone. To store: Keep in an airtight container at room temperature for 4-5 days. It can be kept for up to a week in the refrigerator.