1. In a small mixing bowl, combine the flour, salt, and baking soda; whisk. In another bowl, using a wooden spoon or a mixer, beat the butter and sugar until light-colored and fluffy. Beat in the eggs, one at a time. Stir in sour cream and vanilla. Using a rubber spatula, gently fold in the blueberries.
2. Line a 12-cup muffin tin with the cupcake liners. Using an ice cream scoop or spoon, fill each muffin cup two-thirds full with the batter.
Sprinkle sugar evenly over the top of each muffin.
3. When ready to cook, start the Traeger grill on Smoke with the lid open until the fire is established (4 to 5 minutes). Set the temperature to 375 degrees F and preheat, lid closed, for 10 to 15 minutes.
4. Bake the muffins 25 to 30 minutes, or until a toothpick inserted in the center of one comes out clean (no uncooked batter clinging to it). Serve warm or at room temperature.