Place the butter in a medium skillet over medium heat. Cook, stirring frequently, until the butter becomes a deep amber, 4 to 5 minutes. Remove and let cool.

Preheat the oven to 300ºF and grease a 9-inch square metal baking pan.

In a large bowl, whisk together the almond flour, pecan flour, sweeteners, collagen, baking powder, and salt. Be sure to break up any clumps in the nut flours or sweeteners.

Add the browned butter, egg, egg yolk, and caramel extract. Stir until the dough comes together, then stir in the chopped pecans.

Press the dough evenly into the prepared baking pan and bake 12 to 18 minutes, until the edges are golden and the center is just barely set. They will still be very soft.

Remove and let cool completely before cutting into bars.