Preheat your oven according to the boxed cake directions.
In a large bowl, prepare the cake mix, swapping the water for milk and the oil for melted butter. Stir in the lemon juice and vanilla bean paste until smooth.
Pour the batter into a baking dish and bake according to package directions, until lightly golden and a toothpick inserted into the center comes out clean. Let cool completely.
Meanwhile, make the blueberry compote. Add the frozen blueberries, maple syrup, lemon juice, and salt to a small saucepan over medium heat. Cook for 8–10 minutes, stirring occasionally, until the blueberries burst and the mixture is thick and jammy. Let cool completely.
Mix the cooled blueberry compote into the frosting until fully combined.
Add sprinkles to a plate and set aside. Once the cake has cooled, crumble or cut the cake into pieces and add to mason jars. Top each jar with the blueberry frosting, then dip the frosted tops into the sprinkles. Serve and enjoy!