Preheat oven at 350°F.
In a large bowl, add all the ingredients for the crust and combine well. Mix the dry ingredients first before adding the wet ingredients.
Line a 9.5 inch baking pan with parchment paper. Pour the mixture inside and spread evenly to the edges. Bake at the center of the oven for about 25-30 minutes or until the edges brown and top turn golden brown.
While the crust is baking in the oven, proceed to make the lemon filling.
Zest all four lemon, taking just the yellow part. Then squeeze all the juices out of it. Make sure to filter out the seeds.
In a medium bowl, mix all the dry ingredients for the lemon filling before adding the wet ingredients. Combine and mix until well incorporated.
After the crust is ready and has been cooled down, pour the lemon filling on top. Place back in the oven while still at 350°F and bake for another 20 minutes.
After baking let it cool and sit for at least one hour.
After it's cooled completely, cover and refrigerate for at least 2-3 hours.
When it's ready, take out of the refrigerator and remove the lemon bars from the baking dish and place on a cutting board. Cut into 12 square bars.
Generously sprinkle powdered sweetener for topping.
Serve and enjoy!