Soak the red lentils for at least 4 hours or overnight, then rinse and drain well.
Separate the eggs and whip the whites with a pinch of salt until stiff peaks form.
Blend the lentils with sour cream, egg yolks, maple syrup, and oil until completely smooth.
Stir in shredded coconut, baking powder, and vanilla.
Gently fold in the whipped egg whites to keep the batter light.
Pour into a lined, greased 9½9-inch pan and bake at 350°F (180°C) for about 40 minutes, until set and golden.
Let cool slightly, spread with melted white chocolate, sprinkle with coconut if using, then refrigerate for 1 hour before slicing and serving.
