Combine dressing ingredients in a jar and shake or mix well.
Refrigerate for two hours or longer.
Mix all salad ingredients together and top with dressing.
Notes
This salad is very versatile. You can switch it up by candied pecans, dried cranberries, goat cheese or feta cheese, diced chicken, avocado, or sunflower seeds.
Use fresh spinach. Choose fresh baby spinach for the best flavor and texture. Baby spinach is tender, mild and perfect for salads.
Make the dressing ahead of time. Preparing the homemade red onion dressing a few hours ahead allows the flavors to blend together. Store it in the refrigerator until you're ready to serve.
Shake or whisk the dressing before serving. Homemade salad dressings can separate as they sit. Give the dressing a good shake or whisk to bring everything back together.
Wait to add the dressing. For the freshest salad, toss everything together with the dressing right before serving. Adding it too early can cause the spinach to wilt.
Start with less dressing. Add a little dressing at a time and toss until the spinach is lightly coated. You can always add more, but too much dressing can make the salad soggy.
Prepare ingredients ahead of time. You can wash and dry the spinach, prepare the toppings and make the dressing ahead of time. Store everything separately and assemble just before serving.