Preheat oven to 375F. Toss pumpkin seeds with 1/8 tsp. salt, cayenne pepper, cumin and vegetable oil.
Spread in a single layer on a rimmed baking sheet; roast for 5 minutes, shaking pan halfway through.
Pour into a dish; cool.
Mix juice, shallot, garlic, ginger, vinegar, mustard and honey in a blender until smooth. With motor running, drizzle in olive oil. Season with salt and pepper.
In a salad bowl toss spinach and bell pepper with enough vinaigrette to coat.