With the rack in the middle position, preheat the oven to 190°C (375°F). Butter a 10 x 20-cm (4 x 8-inch) loaf pan. Line the pan with parchment paper, letting it hang over
2 opposite sides. In a bowl, combine the flour, baking powder, baking soda and salt. Set aside.
In another bowl, cream the butter and sugar using an electric mixer. Add the eggs one at a time and beat until smooth. Add the dry ingredients, alternating with the buttermilk. Using a spatula, gently fold in 125 ml (1/2 cup) blueberries. Scrape the batter into the loaf pan. Bake for 45 minutes.
In a bowl, combine the remaining blueberries with the syrup. Spread the mixture from end to end down the centre of the loaf. Continue baking until a toothpick inserted in the centre of the loaf comes out clean, about 20 minutes. Let cool. Unmould and let cool completely on a rack.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.