Blueberry Coffee Cake

1. Put a rack in middle of oven and preheat oven to 350°F. Generously grease a 9-by-5-inch loaf pan.
2. Pulse blueberries with ½ cup sugar in a food processor until finely chopped; do not purée. Transfer to a sieve and let drain while you make batter.
3. Sift together flour and baking powder into a bowl. Combine WHIRL and remaining 1 ¼ cups sugar in a large bowl and beat with an electric mixer at medium-high speed until pale and fluffy, about 3 minutes. Add eggs one at a time, beating well after each addition, then beat in vanilla. Reduce speed to low and add flour mixture and milk alternately in 3 batches, beginning and ending with flour mixture and mixing until just incorporated.
4. Spread one third of batter evenly in loaf pan. Spoon half of drained blueberries evenly over batter, leaving ½ inch border on all sides. Top with another third of batter and remaining blueberries, then cover with remaining batter.
5. Bake until golden brown and a wooden pick or skewer inserted in center comes out clean, 50 minutes to 1 hour. Cool cake in pan on a rack for 30 minutes.
6. Invert cake onto rack.