Get your oven ready by preheating it to 350°F (177°C). Line an 8x8-inch baking dish with parchment paper, leaving an overhang to easily lift the brownies out later.
In a big mixing bowl, simply whisk together the collagen protein powder, tapioca flour, Besti sweetener, and cocoa powder until everything is evenly combined.
Now, add the almond butter, melted butter, room temperature eggs, and vanilla extract (if you're using it). Stir everything together really well until you have a smooth, thick, and somewhat sticky "batter." Don't worry, its thickness is key for that fudgy texture!
Scoop the thick brownie batter into your prepared baking dish. Use a spatula to spread it out evenly, making sure it reaches all the corners.
Bake for about 28-35 minutes, or until the edges look set and a toothpick inserted into the center comes out with just a few moist crumbs on it. (Aim for slightly underdone for extra fudginess, about 30-32 minutes is often perfect.)
Once baked, let your delicious protein brownies cool completely in the pan before slicing and serving. This patience will be rewarded with the best fudgy texture!