Preheat oven to 340°F (170°C).
Line the bottom of an 8X4 inch baking pan then grease using softened butter.
Combine the flour, salt, baking powder into a bowl and whisk together.
Add the butter, brown sugar and granulated sugar into a mixing bowl with the paddle attachment and beat until until fluffy and smooth about 2-3 minutes.
Scrape the sides of the bowl, then add the eggs one at a time beating on medium speed until combined.
Add in the lemon zest, lemon extract and vanilla extract and mix to combine.
Slowly and carefully add the flour mixture alternating with crème fraîche into the to the butter mixture while mixing machine is running on slow speed just until incorporated.
Fold in the blueberries or mixed berry fruit using a spatula.
Pour batter into baking pan and top with some blueberries, Bake for about 60 minutes or until a inserted wood pick comes out clean Alternatively you can use a thermometer, Once the internal temperature of the cake reaches 200°F (94°F) or above, the cake is fully baked.
Remove the loaf cake from the oven and release from baking pan. Cool on wired rack for 40 minutes.
Serve with crème fraîche chantilly whipped cream