First Step: Prep oven and pan

Preheat your oven to 350°F (175°C). Line the bottom of an 8-inch springform pan with parchment paper or grease an 8×8 or 9×9-inch square pan to prevent sticking.

Second Step: Toss blueberries

In a small bowl, gently toss the fresh blueberries with lemon zest and optionally one tablespoon of flour to help prevent sinking. Set aside.

Third Step: Make streusel topping

Whisk together granulated sugar and all-purpose flour for the streusel. Stir in melted butter until the mixture resembles moist sand. Set aside for topping after batter preparation.

Fourth Step: Combine dry cake ingredients

In a medium bowl, whisk cake flour, baking soda, and salt together to ensure even distribution of leavening and seasoning.

Fifth Step: Cream butter and oil

Using a mixer, beat room temperature butter and vegetable oil on medium-high speed for 2-3 minutes until fully combined.

Sixth Step: Add sugar and eggs

Gradually add granulated sugar on low speed, then increase to medium and beat for 1-2 minutes until fluffy. Add eggs one at a time on low speed, mixing well between each addition, scraping down sides as necessary.

Seventh Step: Add flavor extracts

Mix in vanilla and optional lemon extract to the batter for a vibrant citrus aroma.

Eighth Step: Incorporate dry ingredients and milk

On low speed, alternately add half the dry ingredients and half the milk, mixing until almost combined after each addition, then repeat. Avoid overmixing to maintain a tender crumb.

Ninth Step: Add blueberries

Pour batter into the prepared pan and spread evenly. Sprinkle the lemon-zested blueberry mixture over the batter, gently pressing them lightly into the batter to hold them in place.

Tenth Step: Top with streusel

Sprinkle the prepared streusel topping evenly over the blueberries and gently pat down to adhere.

Final Step: Bake and cool

Bake for 40-45 minutes, or until the streusel is golden and blueberries are bubbling. Test doneness with a toothpick; it should come out clean. Cool in the pan for 5-10 minutes, then transfer to a wire rack to cool completely before slicing and serving. Pair with whipped cream or ice cream for a special touch.