Preheat oven to 350 degrees
Lightly butter a 12 inch cast iron skillet or a 9x13 baking dish
In a small bowl, mix sugar and cinnamon. Set aside
Pour both cans of blueberry pie filling into the pan
Add the lemon juice and give a quick stir to combine
Add the blueberries to the top of the filling
Sprinkle the cake mix over the blueberries and filling
With a spoon, gently swirl the cake mix and blueberries together, just to barely mix. There should still be mostly dry cake mix on top.
Dot the top of the cake with the cubed butter
Sprinkle the cinnamon sugar mix over the entire cake, then top with the almonds
Place in the oven and bake for approximatly 50 minutes, or until top is slightly golden
Remove from the oven, allow to cool for 10 minutes, then serve