Preheat oven to 350. Line 8 holes of a standard muffin tin with paper liners and spray with cooking spray.
Stir together the ingredients for the muffins just until they are incorporated. Do not overmix the batter. Gently fold in the blackberries.
Bake for 35-40 minutes until the muffins are golden brown around the edges and feel firm to the touch when pressed gently in the middle. Cool completely.
Stir together the ingredients for the glaze and drizzle over the cooled muffins.
Notes
Nutrition: This recipe makes 8 muffins. There are 3.9 NET carbs per serving.Substitutions: Swap the blackberries for raspberries, chopped strawberries, or blueberries. To Store: Place the muffins in a sealed container. Put in the fridge for up to 4 days or store at room temperature for 2-3 days. To Freeze: Keep in a tightly sealed container or freezer bag for up to 3 months. Thaw before eating.