1. Preheat oven to 400 degrees F and adjust oven rack to middle position.
2. Toss onion wedges with coconut oil. Transfer to baking sheet and roast until brown and soft, about 25 minutes, flipping halfway through cooking. Cool for 15 minutes.
3. Whisk orange and lemon juices, mustard, honey, thyme, salt, and pepper together in a bowl. Gradually whisk in olive oil.
4. Divide Bibb lettuce leaves among individual salad plates. Toss spinach with 1/4 cup dressing in a large bowl. Divide spinach among plates. Arrange roasted onion, pear, goat cheese, and cranberries on top. Drizzle with remaining dressing and serve.