Blueberry Coffee Cake

1 . Stage

Make the topping: Preheat oven to 350°. In a medium bowl, whisk together sugars, cinnamon, and salt. Add melted butter and stir to combine. Add flour and stir until moist clumps form. 

2 . Stage

Make the cake: Butter a 9"-x"-13" baking pan and line with parchment, leaving a 2-inch overhang. Butter parchment. In a medium bowl, whisk 2 1/2 cups flour, baking soda, baking powder, and salt. 

3 . Stage

In a large bowl, beat room-temperature butter and sugar until light and fluffy. Add eggs one at a time, beating until each is well combined. Add flour mixture, sour cream, and vanilla and beat until just combined. 

4 . Stage

In a medium bowl, toss blueberries with remaining 2 tablespoons flour and add to batter. Fold gently, just until blueberries are combined. Scrape cake batter into prepared baking dish and spread top evenly with a spatula. Sprinkle prepared topping evenly over batter. 

5 . Stage

Bake until a toothpick inserted into the center comes out clean, 50 to 60 minutes. Let cool completely. 

6 . Stage

Cut cake into squares and serve slightly warm or at room temperature.