Preheat the oven to 350°F and spray a 9x5-inch loaf pan with gluten-free nonstick cooking spray.
In a large bowl, whisk together the flour, xanthan gum, baking powder, salt, cinnamon, and granulated sugar. Gently stir in the fresh blueberries, then set aside.
In a medium bowl, whisk together the eggs, coconut milk, brown sugar, oil, and vanilla.
Pour the wet ingredients into the dry ingredients. Mix until just combined, then transfer the batter to the prepared baking pan. Sprinkle the top of the bread with the raw sugar, if using.
Bake for 55-65 minutes or until a tester or toothpick comes out clean. Cool in the pan for 20 minutes, then remove the bread from the pan and cool on a wire rack. Cool completely before slicing.
Notes
Keep the bread wrapped tightly in plastic wrap at room temperature for up to 3 days. To freeze, wrap tightly in plastic wrap, then freeze in a freezer-safe bag for up to 3 months.