In a large mixing bowl, or electric stand mixer, beat butter and sugar for approximately 2 minutes until slightly airy (lighter in colour).
Add eggs and vanilla extract, mix until blended.
Add dry ingredients, mix until fully combined.
In a large bowl, add 1 Tbsp of flour and mix in the frozen blueberries with a spoon until the berries are lightly coated.
Fold the lightly flour-coated blueberries into the batter.
Lightly grease a loaf pan and lightly dust the loaf pan with flour.
Add 1/3 of the batter evenly into the loaf pan. The batter will be slightly stiffer to work with from the cold temperature of the frozen blueberries. In spoonfuls, drop chilled apricot coulis over the layer of batter. See my pictures.
Add 1/3 more of the batter evenly into the loaf pan. You may want to do spoonfuls into the pan and gently spread, as the batter is not as runny and harder to spread.
Add one more layer of apricot coulis evenly over the second layer of batter.
Add remaining batter evenly to cover the apricot coulis.
Bake at 350 F for 60-90 minutes with remaining 20 minutes covered with tin foil to avoid over-baking the top of the loaf. The toothpick test should come out clean in the middle of the loaf. Cool completely, preferably overnight, before slicing. Enjoy!!