Preheat oven to 350° and line a 12-cup muffin pan with cupcake liners.
In a large bowl, whisk to combine almond flour, Swerve, baking powder, baking soda, and salt. Whisk in melted butter, almond milk, eggs, and vanilla until just combined.
Gently fold blueberries and lemon zest (if using) until evenly distributed. Scoop equal amounts of batter into each cupcake liner and bake until slightly golden and a toothpick inserted into the center of a muffin comes out clean, 23 minutes. Let cool slightly before serving.