Preheat the oven to 225`c and line a muffin tin with muffin liners. In a small bowl, combine the flour, salt, baking powder and cinnamon. Stir together and set aside. In a medium-sized bowl, whisk together the eggs and sugar until well combined. Add the yogurt, oil and vanilla and whisk to combine. Add the dry ingredients to the wet ingredients and whisk until just incorporated. The batter doesn’t have to be smooth; it’s actually best if there are still some small flour lumps. To the bowl of the dry ingredients, add the blueberries and the extra teaspoon of flour and stir together with a fork until all the berries are coated with flour. Add the coated berries to the batter and fold together with a rubber spatula. Spoon the batter into the prepared muffin cups, filling each cup all the way to the top with batter. Bake in the middle of the oven for 8 minutes, then turn the oven temperature down to 175`c (without opening the oven door) and bake for another 15-20 minutes, or until the muffin tops are golden and firm and a tester inserted into the center of each muffin comes out clean. Take the muffin tin out of the oven and allow the muffins to cool for about half an hour in the tin before taking the muffins out of the pan and placing them on a wire rack to cool completely. To make the glaze, mix together the icing sugar and vanilla with enough lemon juice to make a drizzle. Spoon over the muffins and serve.