Instructions
Step 1
Position a rack in the center of the oven and preheat to 350°F. Lightly grease a 9-inch round cake pan with butter and line with parchment.
Step 2
Make the seed topping: In a small pot over low heat, melt the butter. Add the brown sugar, orange juice and zest, and salt, and cook, stirring continuously, until the sugar is dissolved and the mixture is lightly bubbling, 1–2 minutes. Stir in the pumpkin seeds, sunflower seeds, poppy seeds, and fennel seeds. Pour the seed mixture into the prepared pan, using a silicone spatula to spread the mixture into an even layer. Set aside.
Step 3
Make the cake batter: In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.
Step 4
In another medium bowl, use your fingers to rub the sugar and orange zest together until the mixture is moist and fragrant. Add the yogurt, orange juice, vanilla, and eggs, and whisk to combine.
Step 5
Slowly whisk the dry ingredients into the wet ingredients until just combined. Using a silicone spatula, fold in the oil and poppy seeds until fully incorporated.
Step 6
Carefully pour the batter into the prepared pan, covering the seed mixture. Bake until a tester inserted into the center comes out clean, 35–45 minutes. Allow to cool slightly, then run a butter knife or offset spatula around the edge of the cake to loosen, and invert onto a cooling rack. Remove the parchment, and allow the cake to cool completely before serving.