How to make it :
Preheat the oven to 350°F. Spray a 4 1⁄2 x 8 1⁄2-inch loaf pan with nonstick spray.
Whisk together the flour, lemon zest, baking powder, baking soda, and salt in a medium bowl; set aside. With an electric mixer on medium speed, beat the butter until creamy, about 1 minute. Add the sugar and vanilla and beat until light and fluffy, about 4 minutes. Reduce the speed to low. Gradually beat in the egg substitute. Alternately add the flour mixture and sour cream, beginning and ending with the flour mixture and beating just until blended. Gently fold in the blueberries.
Scrape the batter into the pan; spread evenly. Bake until a toothpick inserted into the center comes out clean, about 1 hour 10 minutes. Let cool in the pan on a rack 10 minutes. Remove the cake from the pan and let cool completely on the rack. Yields 1⁄12 cake per serving.