1. Preheat oven to 325°F (160°C). Prepare a 9x5-inch loaf pan.
2. In a large bowl cream butter and sugar. Add ricotta cheese and beat until combined and smooth. Add eggs, one at the time, beating until combined after each addition. Add lemon zest, lemon juice, vanilla extract and beat until incorporated.
3. Add flour, baking powder, salt and stir until incorporated.
4. Fold in the blueberries.
5. Pour the batter into the pan.
6. Bake for about 60-75 minutes, until a toothpick inserted into the center comes out clean. After 40 minutes of baking, cover with aluminum foil to keep it from browning further. Let cool 10 minutes on a wire rack. Then release from the pan and let cool completely. Dust with powdered sugar (optional).