Premake the pastry base up to a week in advance.
Preheat oven to 160°C.
Spread the lemon butter on the base of the cooked pastry.
Place almonds, caster sugar and lemon zest into the Thermomix bowl and mill 10 sec/speed 8.
Add the eggs and butter and blend until just combined, little lumps of butter are ok, 8 sec/speed 8. Scrape down sides of bowl.
Add the lemon juice and blend again 8 sec/speed 8.
Spread frangipane evenly in the pastry shell on top of the lemon butter layer. Sprinkle with the slivered almonds.
Bake for around 30 minutes or until just set in the centre. It should look cooked but still wobble slightly in the middle.
Dust generously with icing sugar and decorate with edible blooms if you wish.
You can serve this warm or cold, with any of our suggestions.