In a saucepan, melt butter. Add blueberries, orange zest + juice, brown sugar, cinnamon, cloves, and salt.
Cook over medium heat 5–7 minutes, stirring gently until the berries soften and the mixture thickens slightly.
Cool completely before using.
In a saucepan, whisk brown sugar, milk, and salt. Cook until sugar dissolves and slightly thickens. Let cool.
Beat cream cheese + butter until smooth.
Add cooled sugar mixture slowly while whipping until silky.
Mix in vanilla and cinnamon. Chill to thicken before using.
Make the batter: Whisk melted butter + starter until smooth. Add egg, sour cream, vanilla, and orange zest. Fold in flour, sugar, baking powder, and baking soda one at a time. Gently fold in half of the cooled blueberry orange relish.
Bake: Divide into mini cake tins. Bake at 400 °F for 15–20 minutes, checking at 15. Done at 195 °F internal temp.
Finish: Once cooled, pipe cinnamon cream cheese frosting on top, spoon on the remaining blueberry orange relish, and dust lightly with fresh orange zest.
