Preheat the oven to 325°F. Line 6 muffin wells with liners, or use a silicone muffin pan with nonstick spray.
In a medium bowl, whisk together the dry ingredients, then work in the cold butter cubes with your hands until combined.
In a separate bowl, whisk together the wet ingredients, then add to the flour and butter mixture and mix until smooth. Spoon the batter evenly into the 6 wells, about 2 heaping tablespoons each.
Use your spoon to gently round the tops. Combine Erythritol and cinnamon in a small bowl and mix with a fork or spoon. Sprinkle the topping evenly over all 6 muffins, either with your fingers or a small strainer.
Bake until the top is lightly golden and a toothpick or knife inserted in the center comes out clean, 20 to 22 minutes. Allow to rest for 10 to 15 minutes before serving.