Place blueberries in a medium bowl, add 1 tablespoon of flour and toss to coat. Set them aside while you prepare the muffin batter. If you are using frozen berries, keep them cold in the fridge so they don't thaw too much.
Sift flour, baking powder, baking soda, cinnamon, nutmeg and salt into a large bowl. Add granulated sugar and whisk it to blend evenly.
Whisk together eggs, sour cream, oil, milk and vanilla in a medium bowl. Make a well in the center of the dry ingredients and add the liquid mixture. Stir gently using a wide rubber spatula until just combined with some streaks of flour left. Add blueberries and fold them in gently. Do not over-mix. A few small lumps are just fine.
Cover the bowl and set it aside to rest for 30 minutes.
Use a 2 oz scoop or large spoon to divide batter evenly among prepared muffin cups, filling them to the rim. If you want extra tall muffins, and you're willing to wait (if you only have one muffin pan), then you can bake 6 muffins per pan. This allows the hot air to circulate more efficiently around the batter so that it sets quickly around the edges to make the batter rise up instead of out.
Sprinkle the tops generally with coarse raw sugar. Bake for 8 minutes, then lower oven to 350°F and bake for another 12-15 minutes until golden brown and firm to the touch. Transfer pan to a wire rack and let muffins cool for 5 minutes before transferring individually to the rack to finish cooling.