In a large bowl, gently whisk together melted butter, almond flour, crème fraîche, cognac, lemon zest, and sugar until smooth and well-blended;
Add the eggs one at a time, followed by the egg yolks;
Grease a cake pan or porcelain dish, pour in the batter, and smooth the surface for an even finish.
Bake until the cake is golden (40 minutes);
Add 2 tbsp of caster sugar and 1 tsp of water in the same saucepan used to melt the butter. Over medium heat, reduce to a thick syrup consistency, then turn off the heat and stir in the cognac;
Once baked, brush the top of the cake with the cognac glaze then lightly dust the cake with powdered sugar just before serving. Serve in portions or directly from the porcelain dish with a side of crème fraîche and/or berries.
Notes
The smaller the dish, the shorter the baking time;
Choose your baking dish carefully. Metal ones tend to overcook the outside too quickly;
Substitute sugar with stevia or other sweetener at a ratio as directed by the manufacturer.