Preheat your oven to 375°F. Generously butter a 9-inch bundt pan or a 9x5-inch loaf pan.

In a large mixing bowl, cream together the softened butter, granulated sugar, and lemon zest until light and fluffy. Incorporate the sour cream and vanilla extract, mixing until smooth. Beat in the eggs, one at a time, ensuring each is fully blended before adding the next.

Gradually fold in the all-purpose flour, almond flour, baking powder, and kosher salt. Toss the blueberries with 1 tablespoon of flour to prevent them from sinking, then gently fold them into the batter.

For the streusel topping, mix the brown sugar, cinnamon, flour, and butter in a small bowl until a crumbly texture forms.

Spoon half of the cake batter into the prepared pan, spreading it evenly. Drizzle 1 tablespoon of blueberry jam over the batter and swirl lightly. Sprinkle the streusel mixture over the batter, then add the remaining cake batter. Drizzle the remaining 2 tablespoons of jam on top, swirling again for a marbled effect. If desired, sprinkle 1 tablespoon of sugar over the surface for a crisp finish.

Bake the cake for 55–60 minutes, or until the center is set and a toothpick inserted into the middle comes out clean.

While the cake bakes, prepare the glaze by whisking together the powdered sugar, lemon juice, and honey in a bowl until smooth and pourable.

Allow the cake to cool slightly before drizzling the glaze over the top. Slice and serve. Enjoy!