1. Preheat the oven to 375 degrees Fahrenheit. Lightly spray or grease a 12-cup muffin tin.
2. Stir together the milk and lemon juice; let stand for five minutes.
3. In a large bowl, whisk together the flour, baking powder, baking soda, cinnamon and salt; set aside.
4. In a separate bowl, whisk together the soured milk, brown sugar, oil, egg and vanilla until well combined
Pour the wet mixture over the flour mixture and gently stir the two mixtures together, adding the cranberries and flax seeds halfway through.
6. Divide the batter evenly among 10 prepared muffin cups. Evenly sprinkle the sunflower and flax seeds over the batter. Pour water into the empty muffin cups
7. Bake in the center of the preheated oven until the tops spring back when lightly pressed, 20 to 23 minutes. Cool the muffins in the pan on a wire rack for 10 minutes. Remove the muffins from the pan, transferring to a wire rack to cool completely.