Preheat the oven to 350°F (175°C). Lightly coat a loaf pan with oil or nonstick cooking spray so the baked bread can be removed easily.
Combine the ground flaxseed and water in a small bowl. Stir thoroughly, then leave the mixture undisturbed for several minutes until it develops a thick, gel-like consistency.
Place the pumpkin purée, brown sugar, canola oil, prepared flaxseed egg, and soy milk in a large mixing bowl. Whisk until the ingredients form a smooth, evenly blended mixture.
Add the all-purpose flour to the wet mixture. Sprinkle the baking soda, baking powder, salt, cinnamon, nutmeg, and cloves evenly over the flour.
Using a large spoon or spatula, gently fold the ingredients together just until the flour is fully moistened and no dry streaks remain. Avoid excessive mixing, as this can make the finished loaf less tender.
Transfer the batter to the prepared loaf pan and spread it evenly. Scatter the pepitas across the surface.
Place the pan in the preheated oven and bake for approximately 1 hour 15 minutes. The bread is ready when a toothpick inserted into the center comes out clean.
Remove the loaf from the oven and allow it to rest in the pan for 10–15 minutes. Carefully transfer it to a wire cooling rack.
Slice the bread while it is still warm for immediate serving, or allow it to cool completely for neater, more uniform slices.