Begin by melting the butter or coconut oil in a small saucepan over low heat until fully liquefied.
In a large mixing bowl, combine the almond flour, powdered sugar (or erythritol), lemon zest, salt, and baking soda. Mix the dry ingredients together thoroughly.
Once the butter or coconut oil has melted, add the vanilla extract and lemon juice to the mixture. Stir well to combine.
Pour the wet mixture into the bowl with the dry ingredients and mix until a dough forms. If the dough is a bit sticky, don’t worry; it’s meant to be pliable.
Roll the dough into small balls, about 1 inch in diameter. For a chewier texture, you may want to refrigerate the balls for at least 30 minutes, or even overnight if you have time.
If you prefer to bake immediately, roll the dough balls in some additional powdered sugar (or erythritol) if desired.
Preheat your oven to 325°F (160°C) and line a baking tray with parchment paper.
Place the dough balls onto the parchment-lined tray, leaving a bit of space between each ball.
Using the back of a spoon, gently press down each ball to flatten them into cookie shapes.
Bake in the preheated oven for about 10 minutes. Be careful not to overbake; they should be slightly golden at the edges but still soft in the center.
Allow the cookies to cool completely on the tray before transferring them to a wire rack, as they are delicate when warm.