Use a hand mixer or stand mixer to cream the butter with ½ cup of the brown sugar. Beat until it starts to get a bit fluffy.
Beat in vanilla.
Beat in eggs one at a time.
Stir in salt and baking powder.
Stir in 1 cup of the flour until well-incorporated.
Stir in milk.
Add the remaining ½ cup flour and stir until well-incorporated.
Add the remaining ½ cup brown sugar and stir until well-incorporated.
Coat the blueberries in 2 tbsp flour.
Gently fold blueberries into the batter with a spatula.
Line a loaf pan with parchment paper. Transfer the batter to the loaf pan.
Bake for about 1 hour 5 minutes, or until the top is golden brown and a knife comes out clean (recommend checking starting at 50 minutes). Remove from oven.
Allow the bread to cool to room temperature. Remove from the pan by lifting the parchment paper. Peel away parchment paper and slice as desired. Store wrapped tightly in plastic wrap. (The bread can get a little hard overnight, even when wrapped tightly. Microwave for 10 seconds under a damp paper towel, and it'll be good to go!)