Preheat oven to 350°F. Grease a 9×5 inch loaf pan and line the bottom with parchment paper.
Add sugar and lemon zest to a small bowl, and rub them together with your fingers.
Add ricotta cheese, melted butter, lemon sugar, lemon juice, and vanilla extract to a medium bowl. Whisk to combine, and then whisk in the eggs, one at a time.
Add all the flour (setting aside 1 tablespoon), baking powder, and salt to the ricotta cheese mixture and carefully fold the flour mixture with the wet ingredients.
Toss the blueberries with the tablespoon of reserved flour and add to the pound cake batter. Carefully fold the blueberries in with a rubber spatula, then transfer the batter to the prepared loaf pan.
Bake the cake for about an hour or until starting to brown around the edges and a cake tester or toothpick inserted in the center comes out clean.
Allow the cake to cool in the pan on a wire rack for 20-25 minutes. Run a knife around the edge to loosen the cake. Carefully remove the cake from the pan by inverting it onto the rack and then turning it right-side up.