Cut the butter into small cubes and put it in a kitchen robot together with the flour.

Mix on "Pulse" until a dough is formed.

Add the egg (both yolk and white) and mix.

You may need to add a bit of cold water as well, so gradually add one Tbsp until you reach the desired consistency for the tart dough.

Get the dough out of the robot and form a ball. Wrap it in plastic foil and put it in the fridge for 1 hour.

After 1 hour, take out the dough ball and roll it out in a tart pan (I used a 20 cm one). I couldn't find my rolling pin so I greased my pan with a little bit of oil, wet my hands, and pressed the dough directly onto the pan with the help of a glass bottom. The lesson here is: there's always a solution in case you don't have the right utensils, space or if you're lazy like me! :)

Place the tart pan in the fridge.

Add the sour cherries to a pan and set the heat to high/maximum. Cover with a lid. The sour cherries will start to leave their juice in the pan.

Add the coconut sugar and rum and set the heat to medium. After 5 minutes, add the corn starch and mix.

Cook for 5 more minutes without a lid.

Add the sour cherries mix over the tart dough and add the pan to the oven.

Bake at 180C for around 20 minutes or until the dough turns golden.