Methods

1. PREHEAT THE OVEN AND PREP THE PAN. Preheat the oven to 350°F (175°C). Drape a saddle of parchment paper into a 10-inch (25 cm) loaf pan. 
2. PREP THE RUTABAGA. Peel off the outer skin of the rutabaga, then cut each one into quarters for easier handling. Grate the rutabaga on the largest holes of a box grater. Measure out 3 cups (400 g) of shreds and set aside. 
3. WHISK THE WET INGREDIENTS. In a stand mixer fitted with the whisk (or in a large bowl using a handheld mixer), whip the eggs on medium speed until frothy, about 15 seconds. With the mixer on medium-high speed, gradually stream in the granulated and dark brown sugars until the mixture is doubled in size, about 5 minutes. Add the grapeseed oil and vanilla and whip to combine. Remove the bowl from the mixer stand. 
4. ADD THE DRY INGREDIENTS. In a small bowl, whisk together the all-purpose flour, whole wheat flour, baking powder, baking soda, cinnamon, nutmeg, ginger, crushed fennel seeds, and salt. Tip the dry ingredients into the wet ingredients and stir with a spatula until the ingredients are halfway combined and the batter is streaky. 
5. FINISH THE BATTER AND BAKE. Add the grated rutabaga, pecans, and coconut flakes and gently fold into the batter. Pour the batter into the loaf pan. Scatter the turbinado sugar on top. Transfer to the oven and bake until a cake tester comes out dry, about 1 hour.
6. COOL AND SERVE. Let the loaf rest in the pan for 10 minutes, then tug the parchment liner out and transfer the loaf to a cooling rack. Let cool completely before slicing. Store leftovers at room temperature in an airtight container for up to 5 days or tightly wrapped in plastic wrap in the freezer for up to 3 weeks.