Preheat the oven. Set to 325°F (165°C). Line a baking sheet with parchment paper for easy cleanup and to prevent sticking.
Dry the seeds well. If using seeds from a pumpkin, rinse off the pulp and pat very dry with paper towels. Excess moisture leads to steaming instead of crisping.
Toss with oil and spices. In a bowl, mix olive oil, Cajun seasoning, chili powder, cumin, cayenne, smoked paprika, and salt.
If using sugar or honey, add it now. Stir in the pumpkin seeds until evenly coated.
Spread and roast. Arrange seeds in a single layer on the baking sheet. Roast for 18–22 minutes, stirring once halfway.
They should smell toasty and look lightly golden at the edges.
Add the lime finish. While still hot, immediately toss the seeds with lime zest, lime juice, and soy sauce (if using). The warm seeds will absorb the flavors without getting soggy.
Taste and adjust. Add a pinch more salt or a squeeze of lime if needed. For extra heat, dust with a touch more cayenne while warm.
Cool completely. Let the seeds cool on the tray.
They crisp up as they cool, so don’t skip this step.