Grate zucchini. Place in a fine mesh strainer or on an absorbent cloth (cheese cloth works well). Set aside.
Preheat oven to 325°F. Grease loaf pan or line with parchment paper.
In a large bowl, beat butter and stevia until well combined and fluffy.
Add eggs, lemon zest, lemon juice, and sour cream.
Separately, combine almond flour, baking powder and salt. Add to lemon mixture.
Drain the zucchini by pressing firmly into the mesh strainer or absorbent cloth. Release as much moisture as possible. Add to mixture.
Fold in the blueberries.
Add mixture to prepared loaf pan. Bake 65 minutes or until an inserted toothpick comes out clean. Cool before serving.