This tender and soft blueberry lemon coffee cake is packed with fresh blueberries and lemon flavor. Topped with a zesty crumble topping, this simple coffee cake is perfect for brunches, bake sales and parties.
Preheat the oven to 350°F/175°C. Generously grease an 8x8 baking pan and line with parchment paper, making sure the paper is overhanging. This will make it easier to remove the cake.
In a small bowl, whisk together all of the crumb topping ingredients until large and small clumps form. It might be a bit wet but that's fine, it will harden in the fridge! Place in the fridge.
⅓ cup granulated sugar, ⅓ cup light brown sugar, 1 cup all purpose flour, pinch kosher salt, zest of a lemon, 6 tablespoons unsalted butter
In a large bowl, whisk the flour with the baking powder, baking soda and salt. Set aside.
1 ¾ cup all purpose flour, 1 teaspoon baking powder, ¼ teaspoon baking soda, ½ teaspoon kosher salt
In the bowl of a stand mixer or in a large bowl with a handheld electric mixer, combine the butter and sugar until light and fluffy, about 1-2 minutes.
6 tablespoons unsalted butter, ¾ cup granulated sugar
Mix in the egg, vanilla extract and lemon extract.
Add in the sour cream and zest of 1 of the lemons (leave the other one to the side for now!). Mix on medium-low speed until just combined.
zest of 2 lemons, 1 cup sour cream
Pour the dry ingredients in and mix on low speed until just combined.
In a separate bowl, gently toss the blueberries with the zest of 1 lemon and the cornstarch.
1 ½ cups blueberries, 1 tablespoon cornstarch
Gently stir the blueberries into the cake batter.
Pour the cake batter into your prepared pan. Use a small offset spatula to smooth the top out into an even layer.
Take the crumb topping out of the fridge. Sprinkle it on top evenly. If it has hardened too much, you can use a fork to break it up into small pieces.
Bake in the preheated oven for 60-70 minutes. A toothpick inserted should come out clean. If the crumb topping is getting too brown you can tent it with aluminum foil.
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Notes
My recipes have been developed and tested in metric grams. I highly recommend using a weighing scale and measuring out your ingredients the metric way. Salt: If you don’t have kosher salt, halve the amount of salt called for in the recipe. 1 teaspoon kosher salt = ½ teaspoon fine salt. Please note I am using Diamond Crystal Kosher Salt and not Morton Salt, which is a coarse kosher salt. Coarse kosher salt is much too salty for this recipe. Sour Cream: you can swap out the sour cream for full fat Greek yogurt.Blueberries: I've tested this recipe with fresh blueberries but you can also use frozen blueberries, just don't thaw them beforehand. Lemon Glaze: I used the lemon glaze from my blueberry pound cake, you'll want to halve the recipe. Storage: keep the cake in an airtight container in the fridge for up to 4-5 days.