Preheat the oven to 350 degrees. Line a 9x11 inch baking dish with parchment paper.
In a large bowl using an electric mixer, cream the butter and sweetener on high speed for about 2 minutes. With the mixer on medium speed, add the vanilla, eggs, and peanut butter and mix until well combined.
Keep the mixer on medium speed and slowly add almond flour, baking powder, and salt. Mix until combined and dough is in pea sized crumbles.
Spread a little over half of the dough into the prepared pan, reserving the rest of the dough for later. Press the dough down with your fingers or the back of a rubber spatula so that it is even. Par bake for 15 minutes.
While the crust is baking, prepare the filling. Mix all of the berries in a bowl. In a medium saucepan over medium heat, combine 2 cups of the berries and lemon juice.
Bring the berries to a boil and then reduce the heat and simmer for 10 minutes, until the berries are soft.
Take the saucepan off the heat and whisk in swerve and xanthan gum and smash the softened berries. Stir in remaining berries until combined.
When the crust is done par baking, take it out of the oven and spread the filling evenly over the crust all the way to the sides. Crumble the remaining dough onto the top and sprinkle with chopped peanuts. Bake for 25-30 more minutes until the top is golden brown. Remove from the oven and let cool completely.
Using a sharp knife, slice into 15 equal sized squares.
Enjoy chilled or at room temperature. Store leftovers covered at room temperature for up to 2 days or in the fridge for up to a week.
If you would like to use frozen berries, simply swap them out for the fresh berries. Add all of the berries straight to the pot (do not reserve any for the end) and instead of simmering for 10 minutes, simmer for 15-20 minutes before taking off of the heat and whisking in the Xanthan Gum.