Step 1

Whisk flour, brown sugar, oats, cardamom, ginger, turmeric, baking powder, and salt in a small bowl to combine. Drizzle butter over and, using your fingers, work into dry ingredients until butter is absorbed and clumps form. Set streusel aside

Step 2

Place a rack in middle of oven; preheat to 350°. Coat a 9x5" loaf pan with nonstick spray and line with parchment paper, leaving a generous overhang on long sides. Using the grater attachment of a food processor or the large holes of a box grater, grate zucchini. (You should have about 3 cups.) Wrap shredded zucchini in a kitchen towel and wring out as much excess moisture as you can. Transfer to a small bowl and mix in vanilla extract (adding the vanilla here means the zucchini will take on more of its flavor).

Step 3

Place granulated sugar and lemon zest in a medium bowl and, using your fingers, work zest into sugar until sugar starts to clump and mixture is very fragrant, about 1 minute. Add eggs and oil to bowl and whisk to combine. Add grated zucchini and whisk again to incorporate.

Step 4

Using a fine-mesh sieve, sift flour into another small bowl. Add cardamom, ginger, baking powder, and salt and whisk to combine. Add dry ingredients to zucchini mixture and gently fold with a rubber spatula until there are no visible flour streaks remaining and batter is homogeneous. Scrape batter into prepared pan and smooth surface. Scatter reserved streusel evenly on top.

Step 5

Bake zucchini bread, rotating pan halfway through, until a tester inserted into the center comes out clean, 1 hour 30 minutes to 1 hour 45 minutes. Transfer pan to a wire rack and let zucchini bread cool completely in pan.

Step 6

Run a small offset spatula or paring knife around sides of zucchini bread to help loosen, then turn it out onto rack.

Step 7

To serve, cut zucchini bread into thick slices and divide among plates. Top with jam and crème fraîche if desired.