Preheat the oven to 350°F. Lightly grease a 6-cup muffin pan or use a silicone muffin pan.
In a medium bowl, mix together the coconut flour, baking powder and Truvia.
Make a well in the center. Crack the eggs into the well and beat lightly.
Add almond extract and stir.
Add sour cream and make a smooth batter.
Gently fold in blueberries.
Scoop the batter into the prepared muffin cups, filling each about 3/4 full.
Bake the muffins for about 20-25 minutes until the tops have browned. Let them cool for about 5 minutes in the pan, then transfer them to a rack to cool.
Coconut Flour. I've mentioned this in several other recipes, but coconut flour and almond flour are NOT INTERCHANGEABLE. Coconut flour absorbs way more liquid, needs more eggs, and a lot more fat.
Testing for doneness. Sometimes, with coconut flour, it's hard to use the toothpick test to tell if things are cooked through. You could have a toothpick emerge clean--only to find the batter is still liquidy inside. Ovens do vary, so the first time you make these, here's what I suggest. Use the timing specified here. Then, break open a Blueberry Sour Cream Muffin slightly to see if it's done.
Not Almond flour. Do NOT use almond flour for this recipe. I have a LOT of other keto desserts that use almond flour.
Blueberries. If you use too many blueberries, you will have to bake for much, much longer as the batter tends to be too liquid once they start to cook down. Also, be sure not to overmix the blueberries so you don't end up with smurf muffins.