Preheat oven to 325F and line a standard muffin tin with 12 paper liners (I recommend parchment liners for easy release).
In a large bowl, whisk together almond flour, peanut flour, sweetener, whey protein and baking powder. Add eggs, melted peanut butter, melted butter, almond milk and vanilla extract and stir until well combined.
Divide about ⅔ of the batter between prepared baking cups. Using a spoon, create a well in the center of each, pushing the batter slightly up the sides of the cups.
Dollop about 2 or 3 tablespoon jam into the well, then top each muffin with the remaining batter to cover.
Bake 20 to 25 minutes, until golden brown and set on the top. Remove and let cool at least 15 minutes.