Old-Fashioned Blueberry Coffee Cake

Ingredients

• 1/2 cup all-purpose flour
• 1/4 cup plus 2 tablespoons (packed) dark brown sugar
• 1/2 teaspoon kosher salt
• 1/4 cup pecans, toasted, chopped
• 3 tablespoons chilled unsalted butter, cut into 1/4-inch cubes
• nonstick vegetable oil spray
• 1 1/2 cups all-purpose flour
• 1 tablespoon cornmeal
• 1/2 teaspoon baking powder
• 1/2 teaspoon baking soda
• 1/4 teaspoon kosher salt
• 3/4 cup plus 3 tablespoons sugar, divided
• 6 tablespoons (3/4 stick) unsalted butter, room temperature
• 1/2 teaspoon vanilla extract
• 2 large eggs
• 1 cup buttermilk
• 1 tablespoon ground cinnamon
• 2 cups fresh (or frozen, thawed) blueberries (about 10 ounces)
• 1 tablespoon panko (japanese breadcrumbs)