Preheat the oven to 350 degrees F. and line an 8×8” or 9×9” baking dish with parchment paper and give it a light coat of non-stick baking spray; set aside.
In a medium sauce pot, melt the 1/2 C. butter of a medium-high heat.
Remove from the heat and stir in the 1/2 C. sugar, 1/2 C. sweetener, 2 eggs, and 1 Tsp. vanilla; whisk to combine.
Beat in the 1/3 C. cocoa powder, 1/2 C. flour, 1/4 Tsp. salt, and 1/4 Tsp. baking powder.
Transfer the batter to the prepared baking dish and place in the oven to bake for 25-30 minutes.
Once done, remove from the oven to cool slightly.
While the brownies are cooling a bit, whisk together the 3 Tbsp. butter, 2 Tbsp. cocoa powder, 1 Tbsp. honey, 1 Tsp. vanilla, and 1 C. powdered sugar substitute until smooth.
(Feel free to add 1-2 Tbsp. unsweetened almond milk to thin the frosting to your desired consistency.)
Pour and spread the frosting over the top of the warm brownies.
Serve right away to enjoy or store in a cool dry place for up to 3 days.