Preheat the oven at 350°F (175°C). Prepare a 12 hole muffin tin with cupcake liners.
In a bowl, combine eggs, butter, erythritol, salt, baking powder and vanilla. Whisk until fully combined, with a mixer or in a food processor.
Add the almond flour and combine well.
Slowly add heavy cream, so you are left with a grainy, thick batter, but that would still fall off the spoon.
Divide the batter into 2 equal parts. Gently fold in strawberries in one part and blueberries in the other.
Divide the strawberry batter in 6 muffin liners and the blueberry batter into the other 6, filling 3/4 of each muffin liner.
Bake the strawberry muffins and the blueberry muffins until they are brown on the top, for about 20 to 25 minutes. You can insert a toothpick towards the end and if it comes out clean or just with a few crumbles, your muffins are ready.
Cool your muffins for 10 to 15 minutes before servings.