Ingredients
Method
Preheat oven to 350°. Grease a 8x8" glass or metal baking dish with vegetable oil. Line with parchment paper, leaving overhang on all sides. Whisk 1 cup vegetable oil, 2 large eggs, 1¼ cups (250 g) granulated sugar, 1 cup sour cream, and 1 tsp. Diamond Crystal or ½ tsp. Morton kosher salt in a medium bowl until sugar and salt are dissolved, about 2 minutes. Add 1 tsp. baking powder and ½ tsp. baking soda and whisk vigorously until dissolved, about 1 minute.
Add half of 1 pint fresh blueberries, 2 cups (250 g) all-purpose flour, and ½ tsp. ground cinnamon and stir gently with a rubber spatula until flour is incorporated and no streaks remain. Scrape batter into prepared baking dish and smooth surface. Scatter remaining blueberries on top, then sprinkle 1 cup (100 g) store-bought granola over. Lightly press granola into batter to adhere.
Bake cake until topping is golden brown and a tester inserted into the center comes out clean, 55–60 minutes. Transfer pan to a wire rack and let cool 15 minutes. Using parchment paper overhang, lift cake out of pan and onto a cutting board. Cut into pieces to serve. Do ahead: Cake can be baked 1 day ahead. Store tightly wrapped at room temperature.