Wash and dry the lettuce and tear into pieces. You should have about 6 cups. Place in a large salad bowl or large storage container.
Peel the Mandarins with a sharp paring knife over a measuring cup to catch any juices and set the cup aside. Cut the Mandarins in half and slice the halves into rounds.
Top the lettuce with Mandarin and onion slices, feta cheese crumbles and capers.
Make a dressing by whisking all remaining ingredients together in the measuring cup with reserved citrus juice.
Toss with salad ingredients and serve.
Notes
You can prepare this easy salad ahead of time. Mix the dressing ingredients and salad ingredients separately. Whisk or shake the dressing and toss the salad right before serving.This salad is rich in quercetin, a flavonoid whose health benefits include boosting immunity. The vitamin C found in the little Mandarins helps your body absorb both quercetin and the calcium in the greens.I suggest red leaf lettuce as the base of the salad because it is high in quercetin, but any leafy green will taste fine. Arugula and spinach are also good sources of quercetin.If you are short on time, you can substitute canned Mandarin slices for fresh.For extra quercetin-credit, you can add some radicchio, which boasts more than 30 mg of quercetin in 3.5 ounces!