Drain the black-eyed peas, rinse them under cold water, and drain again. Turn the peas into a bowl. Add the onion and spinach, and using two wooden spoons, toss to combine. Drizzle the olive oil, vinegar, and agave syrup or local honey evenly over the top, then sprinkle the thyme, cumin, sea salt, and pepper evenly over the top. Toss well to coat. Taste for seasonings. Serve at room temperature or refrigerate for up to a day. Toss again before serving.