Lemon Blueberry Buckle with Buttery Streusel Topping

Quick Recipe Version (TL;DR)

• Yield: 9 servings
• Prep Time: 20 minutes
• Cook Time: 45 minutes
• Total Time: 1 hour 10 minutes

Quick Ingredients

• 2 cups (250 g) all-purpose flour
• 2 tsp baking powder, 1/2 tsp baking soda, 1/2 tsp fine salt
• 1/2 cup (115 g) unsalted butter, softened (plus more for pan)
• 3/4 cup (150 g) granulated sugar
• 2 large eggs
• Zest of 2 lemons + 1/3 cup (80 ml) fresh lemon juice
• 1 cup (240 ml) buttermilk or whole-milk sour cream
• 2 cups (300 g) fresh blueberries + 1 tbsp flour for tossing
• For streusel: 3/4 cup (150 g) light brown sugar, 3/4 cup (95 g) flour, 1/2 tsp cinnamon, pinch salt, 6 tbsp (85 g) cold unsalted butter

Do This

• 1. Heat oven to 350°F (175°C). Butter a 9-inch square pan and line with parchment.
• 2. Mix streusel: combine brown sugar, flour, cinnamon, salt; cut in cold butter until crumbly. Chill.
• 3. Toss blueberries with 1 tbsp flour; set aside. Whisk flour, baking powder, baking soda, and salt for batter.
• 4. Cream softened butter and sugar until fluffy. Beat in eggs, lemon zest, then lemon juice.
• 5. Mix in dry ingredients and buttermilk alternately, ending with dry. Gently fold in blueberries.
• 6. Spread batter in pan, top evenly with streusel, and bake 40–45 minutes until golden and a tester comes out clean.
• 7. Cool at least 20 minutes before slicing. Serve warm or at room temperature.

---

Why You’ll Love This Recipe

• Tender, moist lemon-scented cake studded with juicy bursts of fresh blueberries in every bite.
• A buttery, cinnamon-kissed streusel topping that melts slightly into the cake as it bakes.
• Simple pantry ingredients and one pan make this perfect for brunch, potlucks, or an easy dessert.
• Flexible recipe: swap dairy options, use frozen berries, or add a lemon glaze if you like things extra citrusy.

Grocery List

• Produce: 2 lemons, 2 cups fresh blueberries (about 1 pint plus a little extra)
• Dairy: Unsalted butter, eggs, buttermilk or whole-milk sour cream
• Pantry: All-purpose flour, granulated sugar, light brown sugar, baking powder, baking soda, ground cinnamon, fine salt, nonstick spray or extra butter for pan

Full Ingredients

For the Lemon Blueberry Batter

• 2 cups (250 g) all-purpose flour
• 2 tsp baking powder
• 1/2 tsp baking soda
• 1/2 tsp fine sea salt (or table salt)
• 1/2 cup (115 g) unsalted butter, at room temperature
• 3/4 cup (150 g) granulated sugar
• 2 large eggs, at room temperature
• Finely grated zest of 2 medium lemons
• 1/3 cup (80 ml) freshly squeezed lemon juice (from about 2 lemons)
• 1 cup (240 ml) buttermilk or whole-milk sour cream, at room temperature
• 2 cups (300 g) fresh blueberries
• 1 tbsp (8 g) all-purpose flour (for tossing with blueberries)

For the Streusel Topping

• 3/4 cup (150 g) packed light brown sugar
• 3/4 cup (95 g) all-purpose flour
• 1/2 tsp ground cinnamon
• 1/4 tsp fine sea salt
• 6 tbsp (85 g) unsalted butter, cold and cut into small cubes

For the Pan (and Optional Finish)

• Butter or nonstick baking spray, for greasing the pan
• Optional: Powdered sugar, for dusting after baking

Step-by-Step Instructions

Step 1: Prep the Pan, Oven, and Ingredients

Preheat your oven to 350°F (175°C) with a rack in the center position.

Grease a 9-inch square baking pan with butter or nonstick spray. For easiest removal, line the bottom and two sides with a strip of parchment paper, leaving an overhang to use as a sling later; lightly grease the parchment as well.

Wash and thoroughly dry the blueberries. Add them to a small bowl and toss with 1 tbsp flour until evenly coated; this helps keep the berries from sinking in the batter.

Finely zest the lemons, then juice them. Measure out 1/3 cup (80 ml) lemon juice and set aside. Bring eggs, buttermilk (or sour cream), and butter to room temperature if they are not already; this helps the batter mix smoothly.

Step 2: Make the Streusel Topping

In a medium bowl, combine the light brown sugar, flour, cinnamon, and salt. Stir with a fork or whisk until no lumps of sugar remain and everything is evenly mixed.

Add the cold, cubed butter. Using a pastry cutter, two knives, or your fingertips, cut the butter into the dry mixture until you have moist, sandy clumps and small pebbles. You are aiming for a mix of fine crumbs and some larger pieces about the size of peas.

Place the streusel in the refrigerator while you mix the batter. Chilling helps it stay crumbly and distinct on top of the cake rather than melting too quickly.

Step 3: Combine the Dry Ingredients for the Batter

In a medium bowl, whisk together the flour, baking powder, baking soda, and salt until well combined. This step evenly distributes the leavening, so you get an even rise and consistent texture.

Set this dry mixture aside; you will add it to the wet ingredients in stages.

Step 4: Cream the Butter, Sugar, and Lemon

In a large mixing bowl (or the bowl of a stand mixer fitted with the paddle attachment), add the softened butter and granulated sugar. Beat on medium speed for 3–4 minutes, scraping down the bowl once or twice, until the mixture is very light, fluffy, and slightly paler in color.

Add the lemon zest and beat for another 30–60 seconds. Rubbing the zest into the sugar and butter releases fragrant lemon oils, giving you a more pronounced citrus flavor.

Beat in the eggs one at a time, mixing well after each addition and scraping down the bowl as needed. The mixture may look a bit curdled when you add the eggs and lemon juice later, but it will smooth out once the dry ingredients are incorporated.

With the mixer on low speed, slowly pour in the lemon juice and mix just until combined. The batter may appear slightly separated at this stage; this is normal.

Step 5: Finish the Batter and Fold in the Blueberries

With the mixer on low speed, add one-third of the flour mixture to the bowl and mix just until blended. Add about half of the buttermilk (or sour cream) and mix briefly. Continue alternating flour and buttermilk, ending with the last portion of flour. Mix only until the batter is smooth and no dry streaks remain; overmixing can make the buckle tough.

Remove the bowl from the mixer. Add the flour-coated blueberries and gently fold them into the batter with a spatula, using broad, sweeping strokes. Try not to crush the berries, and avoid over-stirring so the batter stays light and the blueberries do not turn it purple.

Step 6: Assemble and Bake the Buckle

Scrape the batter into the prepared pan and spread it into an even layer, reaching all the corners. The batter will be fairly thick; use an offset spatula or the back of a spoon to level the surface.

Remove the chilled streusel from the refrigerator and sprinkle it evenly over the top of the batter, covering it from edge to edge. Gently press the streusel down just enough so it adheres to the batter but still sits mostly on the surface.

Bake in the preheated oven for 40–45 minutes, or until the top is deep golden brown and a toothpick or thin skewer inserted into the center comes out with a few moist crumbs but no wet batter. If your oven runs hot and the top is browning too quickly, loosely tent the pan with foil during the last 10 minutes.

Step 7: Cool, Slice, and Serve

Transfer the pan to a wire rack and let the buckle cool in the pan for at least 20–30 minutes. This allows the crumb to set so it slices cleanly while still being pleasantly warm.

Use the parchment sling to lift the buckle out of the pan, if lined, and place it on a cutting board. Slice into 9 generous squares (or 12 smaller pieces).

Dust lightly with powdered sugar just before serving, if desired. Serve warm or at room temperature on its own, or with a dollop of whipped cream, a spoonful of yogurt, or a scoop of vanilla ice cream for dessert.

Pro Tips

• Room-temperature ingredients are key: Soft butter and room-temp eggs help the batter emulsify properly, giving you a tender, even crumb.
• Toss the berries with flour: This little step helps suspend the blueberries throughout the cake instead of letting them sink to the bottom.
• Do not overmix the batter: Once the flour goes in, mix only until no dry streaks remain. Overworking the gluten can make the buckle dense.
• Check doneness early: Ovens vary; start checking at 38–40 minutes. The center should spring back lightly when touched, and a tester should come out mostly clean.
• Let it rest before slicing: It is tempting to cut right in, but a short cooling time keeps the cake from crumbling and lets the streusel set.

Variations

• Lemon glaze finish: Whisk 1 cup (120 g) powdered sugar with 2–3 tbsp lemon juice until pourable. Drizzle over the cooled buckle for extra citrus punch and a glossy finish.
• Mixed berry buckle: Replace up to half of the blueberries with raspberries or blackberries. Keep the total berry amount at about 2 cups.
• Almond twist: Add 1/2 tsp almond extract to the batter and sprinkle 1/3 cup sliced almonds over the streusel before baking for a nutty crunch.

Storage & Make-Ahead

Allow the buckle to cool completely before storing. Cover the pan tightly with foil or transfer slices to an airtight container.

At room temperature: Keeps well for 1–2 days. If your kitchen is very warm or humid, store in the refrigerator instead.

In the refrigerator: Store for up to 4 days. Bring slices to room temperature or warm gently in a 300°F (150°C) oven or in the microwave for 10–15 seconds before serving for the best texture.

Freezing: Wrap individual pieces tightly in plastic wrap, then place in a freezer bag or airtight container. Freeze for up to 2 months. Thaw at room temperature, then refresh in a low oven if desired.

You can also make the streusel up to 2 days ahead and keep it refrigerated in an airtight container until you are ready to bake.

Nutrition (per serving)

Approximate values for 1 of 9 servings:

Calories: 380; Protein: 5 g; Carbohydrates: 53 g; Sugars: 30 g; Fat: 16 g; Saturated Fat: 10 g; Fiber: 2 g; Sodium: 260 mg.