Preheat the oven to 160 °C top bottom heat.
Remove the dough from the refrigerator and roll it out to about 3 mm thick between two sheets of parchment paper.
For small tart rings (8 cm diameter, 2 cm height), cut circles with a 11 cm diameter. The easiest is if you use a 11 cm cookie cutter.
Step after step press the dough into the tart rings using your thumbs, while rotating the tartlet rings.
Trim the excess dough with a sharp knife.
Place the tart rings on a perforated silicone mat onto a baking tray.With the perforated mat there is also no need to blind bake them or to poke holes into the bottom of the tartlets. Bake for 15 minutes.
Take them out of the oven and pipe the almond financier batter into the tartlets almost to the edge.
place thin slices of rhubarb onto the batter.
Bake again for 15 minutes or until the top of the financier is a golden brown color.
Let them cool at room temperature and then in the fridge for 2 hours before continuing.