Zest the lemon into a medium sized saucepan and add in 2 tbsp. of juice from the lemon. Then, add in the sugar and wild blueberries.

Set the mixture over medium heat, stirring occasionally until it comes to a simmer.

In a small bowl, whisk together the corn starch and 1 tbsp. of juice from the lemon. Add the mixture into the jam, stirring constantly until it thickens. Remove the jam from the heat and set it aside.

Preheat the oven to 350°F / 175°C. Generously butter a 9" cake pan. Crumple up some parchment paper, then un-crumple it and place it into the buttered cake pan, making sure it sticks to the bottom and sides. Set aside.

Pour the sugar into a small mixing bowl, then zest the lemon into the sugar. Use your fingers to rub the lemon zest into the sugar.

In a microwave safe bowl, melt the butter. Add the melted butter and flour into the lemon sugar. Use a fork to mix the ingredients together until you have formed little clumps of dough. Set aside.

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

Add the sugar to a medium sized mixing bowl, then zest the lemon into the sugar. Use your fingers to rub the lemon zest into the sugar.

Add in the butter, and beat the mixture with a hand mixer or stand mixer fitted with the paddle attachment for 3-4 minutes, until light and fluffy.

Use a rubber spatula to scrape down the sides of the bowl. Add in both eggs and the vanilla, then beat until well combined.

Add in half of the flour mixture, and mix by hand just until the flour is incorporated. Add in all of the milk and sour cream, and mix until combined. Add in the remaining flour mixture, and lightly fold the mixture together just until there are no more streaks of flour.

Pour the cake batter into the prepared pan and smooth out the top. Gently spread the wild blueberry jam into an even layer over the cake batter, then top it all off with a layer of the lemon streusel.

Bake for 40-50 minutes, until a toothpick inserted in the center of the cake comes out with only a few moist crumbs. Let the cake cool in the pan until it’s no longer too hot to touch, then use the parchment to lift the cake out of the pan.

In a small bowl, whisk together the powdered sugar and lemon juice. Add in more juice as needed for a thinner glaze, if desired.

Once the cake has cooled to room temperature, drizzle the glaze over the top. Serve and enjoy!