📖 Instructions

1. Preheat your oven to 350°F (175°C). This ensures that the oven is heated appropriately so the buckle bakes evenly.
2. Grease and flour a 8-inch square baking pan. This will prevent the cake from sticking and make it easier to remove after baking. Use parchment paper if you like!
3. In a large bowl, cream together ½ cup (1 stick) of softened unsalted butter and ¾ cup of granulated sugar. Use an electric mixer for about 3-5 minutes, until light and fluffy. Ensure the butter is properly creamed with the sugar, scraping down the sides as needed.
4. Beat in 1 large egg. Mix until well combined. Make sure the egg is fully incorporated into the batter. If the mixture looks curdled, add a tablespoon of flour.
5. In a separate bowl, whisk together 1 ½ cups of all-purpose flour, 1 ½ teaspoons of baking powder, and ¼ teaspoon of salt. Combining the dry ingredients separately ensures that the baking powder is evenly distributed.
6. Gradually add the dry ingredients to the wet ingredients, alternating with ½ cup of milk. Begin and end with the dry ingredients. Mix until just combined. Be careful not to overmix; it can lead to a tough cake.
7. Gently fold in 2 cups of fresh blueberries. Distribute the blueberries evenly throughout the batter. I prefer fresh blueberries, but frozen work well too. If using frozen do not thaw.
8. Pour the batter into the prepared baking pan and spread evenly. The batter should fill the pan about ¾ full.
9. Now, make the streusel topping! In a medium bowl, combine ½ cup of all-purpose flour, ½ cup of granulated sugar, ¼ cup (½ stick) of cold unsalted butter (cut into small pieces), and ½ teaspoon of ground cinnamon. It's important that the butter is cold.
10. Use a pastry blender or your fingers to cut the butter into the flour mixture until it resembles coarse crumbs. You can also use two forks to cut the butter in.
11. Sprinkle the streusel topping evenly over the blueberry batter. Make sure to cover the entire surface for maximum crumbly goodness. You can totally add pecans or walnuts into the streusel too, that would be really good!
12. Bake for 45-50 minutes, or until a wooden skewer inserted into the center comes out clean. Start checking for doneness around 45 minutes. Baking times may vary depending on your oven.
13. Let the buckle cool in the pan for 10-15 minutes before cutting into squares and serving. This allows the cake to set slightly and makes it easier to handle.