Preheat oven to 425ºF.
Combine the ground flaxseed with 7 Tbsp. of water and set aside to let thicken slightly, about 5-7 minutes.
Sift together the dry ingredients (flour, baking powder, salt, and cinnamon). Add the sugar and mix well.
In a separate bowl or glass measuring cup, combine the wet ingredients (applesauce, flaxseed mixture, nondairy milk, oil, melted butter, and vanilla).
Add the wet ingredients to the dry ingredients and mix until just combined. Be careful not to overmix!
Fold in the blueberries. Scoop the muffin batter into a lined muffin tin and sprinkle the tops with a pinch of sugar.
Bake the muffins for 5 minutes at 425ºF, then lower the heat to 350ºF without opening the oven door or removing the muffins. Bake an additional 30 minutes until golden brown.