Segui i passaggi nell ordine indicato.
Begin by preheating your oven to 350°F (175°C).
In a mixing bowl, combine the flour, baking powder, and salt. In a separate bowl, whisk together the fruit concentrate, milk, and vanilla extract until well blended.
Pour the wet ingredients into the dry ingredients and gently mix until just combined. Be careful not to overmix the batter.
Place a 9-inch square baking pan in the oven with the margarine or butter. Allow it to melt completely, then swirl the pan to evenly coat the bottom and sides.
Pour the batter into the prepared pan and sprinkle the blueberries evenly over the top.
Bake for approximately 30 to 40 minutes, or until the top is golden brown and a toothpick inserted into the center comes out clean.
While the squares are baking, prepare the glaze. In a small saucepan, combine the apricot jam and orange juice (or water). Heat over low heat, stirring constantly, until the jam is melted and smooth.
Once the blueberry squares are out of the oven, immediately brush the warm glaze evenly over the top.
Allow the squares to cool slightly before cutting into 9 equal portions. Serve warm and enjoy!