Preheat oven to 325F and line an 9x9 or 8x8 inch square baking pan with parchment paper, leaving an overhang for easy removal.
In the bowl of a food processor, combine almond flour, powdered sweetener, and salt. Pulse to combine. Sprinkle with butter pieces and pulse until mixture resembles coarse crumbs. Alternatively, you can cut in butter with a pastry cutter.
Press into bottom of prepared baking pan. Bake 12 to 15 minutes, until just beginning to brown on the edges. Remove and let cool while preparing topping.
In a medium heavy-duty saucepan over medium heat, combine Swerve and butter and stir until Swerve is dissolved. Bring to a boil and cook without stirring until mixture darkens to amber, about 5 to 7 minutes (time may vary depending on the quality of your cookware).
Remove from heat and stir in vanilla extract and salt. If the mixture appears to be separating, stir in 2 tablespoon of powdered Swerve Sweetener until it comes back together.
Sprinkle crust evenly with pecans. Pour toffee mixture evenly overtop. Bake another 15 to 20 minutes, until topping has darkened and bubbles thickly. Let cool completely before cutting into bars.