For a richer flavor, try using browned butter instead of olive oil. If you don't have golden raisins, regular raisins or dried cranberries can be substituted. A squeeze of fresh lemon juice at the end can brighten the flavors even more. To ensure even cooking, avoid overcrowding the pan. You may need to sauté the spinach in batches. Serve immediately as a side dish to complement grilled chicken, fish, or pasta.