Preheat the oven to 325 degrees. Grease an 8x8" baking pan.
Melt the coconut oil. Set aside to cool slightly.
In a small bowl, combine flour, baking powder, and salt.
In a large bowl, combine the melted coconut oil, protein shake, coconut sugar, and maple syrup, and stir until smooth. Add the eggs, vanilla, and lemon juice and mix well. Add the dry ingredients and stir until just combined. Spread the batter in the prepared pan.
Melt the ¼ cup butter for the cinnamon swirl. Add the sugar and cinnamon and stir to combine. Drizzle the cinnamon sauce over the blondie batter and use a butter knife to swirl it in.
Bake for 35 minutes, until a toothpick inserted in the center comes out with just a few crumbs on it. While the cinnamon roll blondies cool, make the cream cheese icing (optional). In a small saucepan over medium low heat, combine the cream cheese, protein shake, powdered sugar, vanilla, and salt, whisking constantly until everything is melted and combined. Take off the heat and allow to cool. Once the blondies are cool, drizzle with the cream cheese glaze.