Preheat oven to 180°C (356F) and line a 9x4" loaf pan with parchment paper.
Sift and mix flour, baking powder, cinnamon, and salt, in a large bowl and set aside.
Place mascarpone and sugar in a large mixing bowl of a stand mixer fitted with the paddle attachment. Mix on medium speed for 1 minute until fluffy.
Add lemon zest, vanilla extract and eggs, one by one, mixing well after each addition. Add lemon juice (it's fine if the batter curdles slightly).
Add dry ingredients in two additions, mixing until just combined. Do not overmix. Fold in blueberries.
Transfer batter to loaf pan and bake for 40-50 minutes or until a skewer inserted into the center comes out clean.
Allow to cool for 5-10 minutes, then transfer to a baking rack to cool completely.