Place butter in a small sauce pan and heat on low until melted. Set aside.
In a mixing bowl, whisk the flour, baking soda and sugar. Make a well and add the eggs. Gently start mixing inwards going outwards with your mini whisk. Add the cooled melted butter and the buttermilk, a splash at a time while continuing mixing. Mix until it is all incorporated.
Pour your batter into your Flexipan®. Evenly spread with your spatula, arrange the raspberries and sprinkle sugar on top.
BAKE!
Bake for 40 minutes at 350F/180C. (Every oven heats differently, monitor your cake from 35min). It is ready when the toothpick inserted comes out clean.
Once your Raspberry Buttermilk Breakfast Cake is out of the oven, let it cool down for about 10min. Then, Unmold and enjoy. Bon Appétit!