Butter your bundt pan, heavily. It may take more than two tablespoons. Place in freezer.
Mix together almond flour, coconut flour, salt, baking powder, xanthan gum, Swerve granulated. Set aside.
Beat Eggs for 3 to 5 minutes.
Stream in melted butter.
Add lemon extract.
Add sour cream, lemon juice and zest.
Add dry mixture and mix just until mixed. Don't over mix.
Heavily butter bundt cake and freeze.
Pour batter into bundt pan only 1/4 way before adding blueberries. Add more batter and berries, but don't have any berries at the top, which ends up being the bottom of the cake.
Bake for 30 to 35 minutes at 325 degrees F., 180 C. Use a meat thermometer to test the center of the cake which should be 207 degrees F.
Once out of the oven, set the timer for 15 minutes. Gently take a knife around the edges of the bundt cake.
After 15 minutes, take a knife again around the edges. Using a flat plate or cake board, using both hands flip cake over. Allow to cool before glazing.