Preheat the oven to 350 degrees and grease a 9-10 inch skillet or baking dish with coconut oil.

In a large saucepan, combine the oats, milk, maple syrup, vanilla, cinnamon and salt and bring to a simmer. Cook over medium heat, stirring occasionally, until thickened to a soft porridge consistency, about 15 minutes. Remove from the heat and allow to cool slightly, about 5 minutes or longer if that's easier.

Working quickly, stir the egg yolks into the oatmeal until well blended. Stir in the blueberries and lemon zest.

In a large bowl or stand mixer whisk the egg whites at medium speed until medium-stiff peaks form, about 2-3 minutes. Using a spatula, gently fold the whites into the oatmeal just until combined. You don't want to see big clumps of white, but you don't want to deflate all the egg whites either.

Pour the mixture into the prepared skillet and bake for about 30 minutes, until golden and puffed. If using a non-dairy milk, the souffle will not get as golden. Serve warm with blueberry sauce, fresh fruit or maple syrup.