Grate the zest of an organic lemon.
Dissolve the dry yeast in the lukewarm water.
Whisk together the butter, the sugar, the eggs, the lemon zest & a pinch of salt w/ your handheld electric mixer until smooth.
Fold in the flour & the yeast mix. You'll get a rather soft & runny mess.
Let the mess rise in a warm place covered w/ a dishcloth for about 90-120 min. The mess will double its volume.
Preheat the oven to 200° C w/ fan.
Dump the mess in a buttered tart form.
Add some bits of butter all over the mess. Sprinkle w/ the sugar & the almond flakes.
Let it bake in the preheated oven for about 15-20 min.
Serve in the tart form.