Preheat your oven to 350°F. Line an 8 x 4 inch loaf pan with parchment paper.
In a large bowl, add butter and erythritol. Whisk until evenly combined. Add eggs, one at a time, whisking after each addition.
Add in lemon juice, zest and vanilla. Whisk until evenly combined.
Add in almond flour, coconut flour, baking powder. Whisk until evenly mixed. Your batter should be thick.
Pour batter into prepared pan. Tap the bottom of the pan a few times against your counter to settle and spread the batter evenly across the pan.
Bake cake in the middle of your oven for about 40-45 minutes or until toothpick inserted comes out clean. Mine were done between 43-45 minutes each time. Let cake cool before drizzling with glaze.
To make the lemon glaze, whisk together all ingredients. If the glaze is too thin, add more powdered erythritol until it reaches your desired thickness. Drizzle over the cake.
The nutrition information provided are only estimates based on an online nutritional calculator. This is not a comprehensive list of all the nutrients in the recipe (i.e., does not include vitamins, cholesterol, etc). I am not a certified nutritionist. Please consult a nutritionist or doctor for accurate information and any dietary restrictions and concerns you may have.