Preheat oven to 350ºF and adjust rack to middle position. Line a muffin tin with unbleached muffin cups. Place butter, sour cream, eggs, vanilla, lemon juice and maple sugar in a bowl and whisk to combine. In a separate bowl, combine the almond flour, coconut flour, gelatin, sea salt, baking powder, and lemon zest. Pour the dry ingredients into the wet ingredients and stir to combine. Stir in the poppy seeds.
Divide the muffin batter evenly into the muffin cups. Bake for 23-25 minutes until just turning golden brown on top.
Note: I only test the recipes on my site with the listed ingredients and measurements. If you would like to try a substitution, you are welcome to share what you used and how it turned out in the comments below. Thanks!