Low Carb Gluten Free Cake Bars

We made these cake bars in my Food Service Management class the other day (best class ever, legit all we do is make a ton of food and eat all of it!) I'm not a huge fan of desserts, but MAN these were delicious!!! I know there is heavy cream still in the frosting, so I'm going to try to find a good substitute for it when I make them at home but for now here's the recipe.

Ingredients:
2 cups almond flour
2 cups hazelnut flour
1/4 cup gluten-free oat flour
1 tsp baking powder
1/2 tsp salt
12 tablespoons margarine, softened
24 packets truvia
2 large eggs
1 tsp vanilla extract
Frosting-
6 tablespoons margarine, softened
monk fruit packets to taste (nectresse)
3 to 5 tablespoons heavy cream
1/2 teaspoon vanilla

Preheat oven to 325 and line a 9x13 inch pan with parchment paper. In a medium bowl, whisk together the almond flour, oat flour, baking powder and salt.  In a large bowl, beat butter and truvia until creamy.  Beat in the eggs and vanilla extract, and then beat in almond and hazelnut flour mixture until dough comes together.  Press dough firmly into prepared pan and smooth top with a flat-bottomed glass. Bake 30 minutes, until just golden brown around the edges and slightly more firm to the touch.  Remove and let cool in pan.

For the frosting:
Beat together butter and 10 packets of monk fruit.
Add cream, 1 tablespoon at a time, until desired consistency is achieved.  Stir in vanilla. Taste, and if not sweet enough, add more monk fruit packets until desired sweetness is reached.  Spread onto cooled bars.
**We had pureed beets lying around from another recipe and we added a little bit to the frosting, and it tasted so good, but not everyone has pureed beets lying around haha.