Preheat the oven to 350°F and butter and line with parchment an 8-inch (20-cm) square baking dish. Set aside.

In a small bowl, combine the flour, brown sugar, granulated sugar, and cinnamon. Cut in the butter with a fork or pastry blender until the mixture is crumbly. Set aside.

In a small bowl, whisk together the flour, baking powder, cinnamon, salt, and baking soda. Set aside.

In the bowl of a stand mixer fitted with a paddle attachment (or with a medium bowl and a handheld electric mixer), beat the sugar, butter, and lemon zest on medium-high speed until light and fluffy, about 2 minutes.

Lower the speed to medium-low and beat in the eggs, one at a time, followed by the buttermilk. Scrape down the sides of the bowl and beat for another few seconds to make sure the batter is evenly combined.

Add in the flour mixture in 3 increments with the mixer on low until just combined, scraping down the sides of the bowl once or twice.

Fold in the blueberries, then spread evenly in the prepared baking dish and sprinkle the topping over the cake.

Bake for 55 to 60 minutes, until the topping is nicely browned and a skewer inserted in the center comes out with a few moist crumbs still attached.

Let cool to room temperature in the baking dish before serving.

Store in an airtight container at room temperature for 2 days.