Grease a 9 inch springform pan with butter and sprinkle with flour, turn pan upside down and tap to remove any excess flour 

Stir blueberries, 2 T sugar and nutmeg together gently in a large bowl

In another bowl, mix 1 1/2 C flour, poppyseeds, baking soda and salt

In a stand mixer or another large bowl, beat butter and 1/2 C sugar until light and fluffy

Add egg and lemon zest, mix thoroughly

Add flour mixture alternatively with the creme fraiche starting and ending with 1/3 of the flour, mix until the flour is incorporated into the batter 

Spread the dough in the prepared pan, bringing the dough about 1 inch up the sides of the pan, making a well in the center

Stir 1 T of flour into the blueberries and pour into in the center well of the dough

Bake for 45 to 50 minutes at 350 degrees

While cake is still warm, drizzle with a glaze made of powdered sugar, lemon juice and enough milk to thin it so it will pour easily

Let cake cool before removing from pan