Preheat oven to 325F and line a muffin tin with parchment or silicone liners.
Combine sour cream, eggs, and vanilla extract in a large blender jar. Blend about 30 seconds.
Add the almond flour, sweetener, baking powder, cinnamon, and salt. Blend again until smooth, about 30 seconds to a minute. If your batter is overly thick, add 1/4 to 1/2 cup of water to thin it out (different brands of almond flour can vary).
By hand, stir in cranberries, keeping a few for the top of the muffins, and chopped pecans if using. Divide the mixture among the prepared muffin cups and bake 25 to 30 minutes, until just golden brown and firm to the touch.