Preheat the oven to 350 degrees Fahrenheit and line a bread loaf pan with parchment paper.

Whisk the melted butter, eggs, and lemon juice together in a mixing bowl until well-combined and creamy (wet ingredients).

In a separate mixing bowl, stir together the almond flour, coconut flour, sugar-free granulated sweetener, baking powder, baking soda, and sea salt (the dry ingredients) until well-combined.

Pour the dry ingredients into the mixing bowl with the wet ingredients and stir until a thick batter forms. Stir in the lemon zest until combined.

Transfer the pound cake batter to the prepared loaf pan and smooth it into an even layer.

Bake on the center rack of the preheated oven for 15 minutes. Remove the pound cake from the oven, turn the oven temperature down to 330 degrees F, and cover the pound cake with foil. Bake for another 50 to 65 minutes at 330 degrees, or until the cake tests clean.

Allow the pound cake to cool completely (at the very least, allow it to cool for 30 minutes) before covering it with glaze and slicing.

To make the glaze, simply stir together the sugar-free confectioners sweetener and the lemon juice together in a small bowl until thick and creamy. Spread all of this mixture on top of the bread. Allow the glaze to set up before slicing into the cake and serving.