In a large pot over high heat, add blueberries, white sugar, and lemon juice. Bring to a boil, mash blueberries, and cook for about 10 minutes until thickened. Let the jam cool completely.
Make the Vanilla Cake
In a medium bowl, combine vegetable oil, greek yogurt, eggs, white sugar, and vanilla extract. Beat until fully combined.
Add flour, baking powder, baking soda, and salt. Slowly mix in milk until fully combined.
Bake the Cake
Pour batter into a lined 8x8 inch baking pan and add half of the jam. Swirl with a knife and bake at 350°F for 30-32 minutes. Cool completely.
Make the Frosting
In a large bowl, mix cream cheese, powdered sugar, and vanilla extract. In another bowl, whip heavy cream until stiff peaks form, then fold into cream cheese mixture.
Assemble the Cake
Spread frosting over the cooled cake, swirl in the remaining jam, and top with blueberries.
Slice and enjoy!
Notes
The cake can be made a day in advance and stored in the refrigerator.