Blend mayonnaise, canola oil, pumpkin seeds, water, vinegar, Cotija cheese, roasted chile peppers, garlic, salt, and pepper in a blender until smooth, about 1 minutes. Add cilantro in batches, blending each to incorporate completely before adding the next, 30 to 60 seconds per batch.

Pour dressing into an air-tight container and refrigerate at least 1 hour before serving.