Prepare and bake the tart dough. If you are going to bake our Tart dough, you can click on the ingredient on the left and follow the instructions.
Wash the blueberries under running water and drain them well. In a bowl mix together 20g / 0.7 oz of sugar, freshly grated lemon zest and freshly squeezed juice of ½ lemon. Add 100g / 3.5 oz of blueberries and give it a good toss. Set aside until needed.
In a mixing bowl whip together mascarpone, greek yogurt, vanilla beans and rum to get a soft, light and shinny texture. In another bowl whisk the whipping cream with 40g / 1.4 oz of sugar until soft peak forms. You should not whisk too much. Add 1/3 of the whipping cream to the mascarpone - yogurt mixture and combine well, using a spatula. Gently fold in the rest of the whipping cream, so that you get a light and airy cream.
Gently pour 2/3 of the cream into the prebaked tart crust. Spread the cream evenly using a flexible spatula. Add sugar coated blueberries (from step 1) to the remaining 1/3 of the cream and stir to combine to release the juice and flavor from the berries. Spread the blueberry cream over the top of the tart. Arrange the blueberries to your liking, we like to completely cover the tart filling. Refrigerate for 1 hour and serve. You can sprinkle with some icing sugar if you like.