Start mixing all the dry ingredients in a bowl: salt, flour, baking powder and baking soda.
Next mix the creme fraiché or fresh cream with some vinegar drops, a lemon juice tablespoon and a pinch of salt.
Using the recipient where we will prepare our muffins batter we start mixing the eggs, vanilla and flour, we can whisk by hand or using an electric whisk.
Now add the creme fraiché and keep whisking until all the ingredients mix together.
With the help of a spatula or spoon and trying not to break all the blueberries add the fresh or freeze blueberries.
If you are going to use a muffin tin grease it or prepare muffin cups and fill them 3/4 of its capacity, to avoid the muffins to spill over the tins.
Let the batter rest for 30 minutes into the fridge before baking.
Prepare the crumble mixing with your fingers the lemon zest, flour, white sugar and butter. Cover generously your muffins with the crumble.
Preheat your oven 180º Celsius (356 Fahrenheit).
Bake your blueberry muffins for 20-30 minutes, depending on your oven, until the crumble browns.