Preheat the oven to 375°F. Spray a loaf pan with cooking spray.
In a large bowl, stir together the flour, brown sugar, baking powder, and sea salt.
Add the orange zest and mix it into the dry ingredients.
Place the Craisins in a small bowl. Sprinkle with a little flour and separate the pieces gently with your fingers. Add them to the flour mixture and stir to distribute.
Make a well in the center of the dry ingredients. Open the pumpkin beer and pour it in all at once. The mixture will foam.
Add the Grand Marnier and stir briskly, just until the ingredients are combined, about 20 strokes. The batter should remain slightly lumpy.
Pour the batter into the prepared loaf pan and drizzle the melted butter evenly over the top.
Bake for 35–45 minutes, or until the top is crusty and a toothpick inserted into the center comes out clean.
Let the bread rest in the pan for 5 minutes, then turn it out onto a wire rack.
Serve warm or at room temperature. Toast slices with butter or apple butter, or finish the cooled loaf with an orange glaze if desired.